Attachment 348500 Details for Bug 188043 – WIP Patch

[patch] WIP Patch

scroll-behavior.patch (text/plain), 102.21 KB, created by Frédéric Wang (:fredw) on 2018-08-30 09:02:08 PDT

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Description:

Filename:

MIME Type:

Creator: Frédéric Wang (:fredw)

Created: 2018-08-30 09:02:08 PDT

Size: 102.21 KB

patch

obsolete

>diff --git a/Source/JavaScriptCore/Configurations/FeatureDefines.xcconfig b/Source/JavaScriptCore/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..211a58e967f 100644
>--- a/Source/JavaScriptCore/Configurations/FeatureDefines.xcconfig
>+++ b/Source/JavaScriptCore/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_SMOOTH_SCROLLING = ENABLE_CSSOM_SMOOTH_SCROLLING;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_SMOOTH_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>diff --git a/Source/WTF/wtf/FeatureDefines.h b/Source/WTF/wtf/FeatureDefines.h
>index 5e1291d20d3..65c0b3be45e 100644
>--- a/Source/WTF/wtf/FeatureDefines.h
>+++ b/Source/WTF/wtf/FeatureDefines.h
>@@ -361,6 +361,10 @@ the public iOS SDK. See <https://webkit.org/b/179167>. */
> #define ENABLE_ACCELERATED_OVERFLOW_SCROLLING 0
> #endif
> 
>+#if !defined(ENABLE_CSSOM_SMOOTH_SCROLLING)
>+#define ENABLE_CSSOM_SMOOTH_SCROLLING 1
>+#endif
>+
> #if !defined(ENABLE_APNG)
> #define ENABLE_APNG 1
> #endif
>diff --git a/Source/WebCore/CMakeLists.txt b/Source/WebCore/CMakeLists.txt
>index cd789311c34..2bdd74fed16 100644
>--- a/Source/WebCore/CMakeLists.txt
>+++ b/Source/WebCore/CMakeLists.txt
>@@ -1031,6 +1031,13 @@ else ()
>     set(ANGLE_FORWARDING_HEADERS_DIR "${FORWARDING_HEADERS_DIR}/ANGLE")
> endif ()
> 
>+if (ENABLE_CSSOM_SMOOTH_SCROLLING)
>+    list(APPEND WebCore_IDL_INCLUDES
>+        page/ScrollBehavior.idl
>+        page/ScrollOptions.idl
>+    )
>+endif ()
>+
> if (ENABLE_GAMEPAD)
>     list(APPEND WebCore_INCLUDE_DIRECTORIES
>         "${WEBCORE_DIR}/Modules/gamepad"
>diff --git a/Source/WebCore/Configurations/FeatureDefines.xcconfig b/Source/WebCore/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..211a58e967f 100644
>--- a/Source/WebCore/Configurations/FeatureDefines.xcconfig
>+++ b/Source/WebCore/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_SMOOTH_SCROLLING = ENABLE_CSSOM_SMOOTH_SCROLLING;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_SMOOTH_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>diff --git a/Source/WebCore/DerivedSources.make b/Source/WebCore/DerivedSources.make
>index a5fdb3edc7a..02775096461 100644
>--- a/Source/WebCore/DerivedSources.make
>+++ b/Source/WebCore/DerivedSources.make
>@@ -790,6 +790,8 @@ JS_BINDING_IDLS = \
>     $(WebCore)/page/PerformanceTiming.idl \
>     $(WebCore)/page/RemoteDOMWindow.idl \
>     $(WebCore)/page/Screen.idl \
>+    $(WebCore)/page/ScrollBehavior.idl \
>+    $(WebCore)/page/ScrollOptions.idl \
>     $(WebCore)/page/ScrollToOptions.idl \
>     $(WebCore)/page/UserMessageHandler.idl \
>     $(WebCore)/page/UserMessageHandlersNamespace.idl \
>diff --git a/Source/WebCore/PAL/Configurations/FeatureDefines.xcconfig b/Source/WebCore/PAL/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..211a58e967f 100644
>--- a/Source/WebCore/PAL/Configurations/FeatureDefines.xcconfig
>+++ b/Source/WebCore/PAL/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_SMOOTH_SCROLLING = ENABLE_CSSOM_SMOOTH_SCROLLING;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_SMOOTH_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>diff --git a/Source/WebCore/Sources.txt b/Source/WebCore/Sources.txt
>index aaf936eff64..254577bdf0b 100644
>--- a/Source/WebCore/Sources.txt
>+++ b/Source/WebCore/Sources.txt
>@@ -3163,6 +3163,14 @@ JSXPathNSResolver.cpp
> JSXPathResult.cpp
> JSXSLTProcessor.cpp
> 
>+#if ENABLE_CSSOM_SMOOTH_SCROLLING
>+
>+JSScrollBehavior.cpp
>+JSScrollOptions.cpp
>+page/ScrollOptions.cpp
>+
>+#endif
>+
> #if ENABLE_GAMEPAD
> 
> JSGamepad.cpp
>@@ -3175,6 +3183,12 @@ Modules/webvr/GamepadWebVR.cpp
> 
> #endif
> 
>+#if ENABLE_CSSOM_SMOOTH_SCROLLING
>+
>+platform/ScrollAnimationSmooth.cpp
>+
>+#endif
>+
> #if ENABLE_LEGACY_ENCRYPTED_MEDIA
> 
> JSWebKitMediaKeyMessageEvent.cpp
>diff --git a/Source/WebCore/SourcesGTK.txt b/Source/WebCore/SourcesGTK.txt
>index 4626b6fcbe5..276d15a7144 100644
>--- a/Source/WebCore/SourcesGTK.txt
>+++ b/Source/WebCore/SourcesGTK.txt
>@@ -56,7 +56,9 @@ page/scrolling/coordinatedgraphics/ScrollingStateNodeCoordinatedGraphics.cpp
> page/scrolling/generic/ScrollingThreadGeneric.cpp
> 
> platform/ScrollAnimationKinetic.cpp
>+#if !ENABLE_CSSOM_SMOOTH_SCROLLING
> platform/ScrollAnimationSmooth.cpp
>+#endif
> platform/UserAgentQuirks.cpp
> 
> platform/geoclue/GeolocationProviderGeoclue.cpp
>diff --git a/Source/WebCore/WebCore.xcodeproj/project.pbxproj b/Source/WebCore/WebCore.xcodeproj/project.pbxproj
>index 20e2892663a..954c4aa56ca 100644
>--- a/Source/WebCore/WebCore.xcodeproj/project.pbxproj
>+++ b/Source/WebCore/WebCore.xcodeproj/project.pbxproj
>@@ -2333,6 +2333,8 @@
> 		833B9E341F508D8500E0E428 /* JSFileSystemEntry.h in Headers */ = {isa = PBXBuildFile; fileRef = 833B9E2A1F508D8000E0E428 /* JSFileSystemEntry.h */; };
> 		833B9E361F508D8500E0E428 /* JSFileSystemFileEntry.h in Headers */ = {isa = PBXBuildFile; fileRef = 833B9E2C1F508D8000E0E428 /* JSFileSystemFileEntry.h */; };
> 		83407FC11E8D9C1700E048D3 /* VisibilityChangeClient.h in Headers */ = {isa = PBXBuildFile; fileRef = 83407FC01E8D9C1200E048D3 /* VisibilityChangeClient.h */; settings = {ATTRIBUTES = (Private, ); }; };
>+		834476EF1DA5BC5E002B6EB0 /* JSScrollBehavior.h in Headers */ = {isa = PBXBuildFile; fileRef = 83E9B3011DA5A51E00FFE8D4 /* JSScrollBehavior.h */; };
>+		834476EF1DA5BC5E002B6EC1 /* JSScrollOptions.h in Headers */ = {isa = PBXBuildFile; fileRef = 83E9B3011DA5A51E00FFE8E5 /* JSScrollOptions.h */; };
> 		834476EF1DA5BC5E002B6ED2 /* JSScrollToOptions.h in Headers */ = {isa = PBXBuildFile; fileRef = 83E9B3011DA5A51E00FFE8F6 /* JSScrollToOptions.h */; };
> 		8348BFAC1B85729800912F36 /* ClassCollection.h in Headers */ = {isa = PBXBuildFile; fileRef = 8348BFAA1B85729500912F36 /* ClassCollection.h */; };
> 		834DFAD01F7DAE5D00C2725B /* SharedStringHash.h in Headers */ = {isa = PBXBuildFile; fileRef = 834DFACC1F7DAE5600C2725B /* SharedStringHash.h */; settings = {ATTRIBUTES = (Private, ); }; };
>@@ -2405,6 +2407,8 @@
> 		83C1D436178D5AB500141E68 /* SVGPathSegMovetoRel.h in Headers */ = {isa = PBXBuildFile; fileRef = 83C1D424178D5AB400141E68 /* SVGPathSegMovetoRel.h */; };
> 		83C1F5941EDF69D300410D27 /* QualifiedNameCache.h in Headers */ = {isa = PBXBuildFile; fileRef = 83C1F5921EDF69D300410D27 /* QualifiedNameCache.h */; };
> 		83C45B8E1DC2B68A008871BA /* ValidationBubble.h in Headers */ = {isa = PBXBuildFile; fileRef = 83C45B8D1DC2B67C008871BA /* ValidationBubble.h */; settings = {ATTRIBUTES = (Private, ); }; };
>+		83C5795D1DA5C301006FAC86 /* ScrollBehavior.h in Headers */ = {isa = PBXBuildFile; fileRef = 8350C3E71DA59B6200356424 /* ScrollBehavior.h */; settings = {ATTRIBUTES = (Private, ); }; };
>+		83C5795D1DA5C301006FAC97 /* ScrollOptions.h in Headers */ = {isa = PBXBuildFile; fileRef = 8350C3E71DA59B6200356435 /* ScrollOptions.h */; settings = {ATTRIBUTES = (Private, ); }; };
> 		83C5795D1DA5C301006FACA8 /* ScrollToOptions.h in Headers */ = {isa = PBXBuildFile; fileRef = 8350C3E71DA59B6200356446 /* ScrollToOptions.h */; settings = {ATTRIBUTES = (Private, ); }; };
> 		83D35AEC1C7187FA00F70D5A /* XMLHttpRequestEventTarget.h in Headers */ = {isa = PBXBuildFile; fileRef = 83D35AEA1C7187ED00F70D5A /* XMLHttpRequestEventTarget.h */; };
> 		83D35AF21C718D9000F70D5A /* JSXMLHttpRequestEventTarget.h in Headers */ = {isa = PBXBuildFile; fileRef = 83D35AF01C718D8400F70D5A /* JSXMLHttpRequestEventTarget.h */; };
>@@ -9770,6 +9774,11 @@
> 		834DD4F31BE08989002C9C3E /* PageMac.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = PageMac.mm; sourceTree = "<group>"; };
> 		834DFACC1F7DAE5600C2725B /* SharedStringHash.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = SharedStringHash.h; sourceTree = "<group>"; };
> 		834DFACE1F7DAE5700C2725B /* SharedStringHash.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = SharedStringHash.cpp; sourceTree = "<group>"; };
>+		8350C3E71DA59B6200356424 /* ScrollBehavior.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ScrollBehavior.h; sourceTree = "<group>"; };
>+		8350C3E81DA59B6200356424 /* ScrollBehavior.idl */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = ScrollBehavior.idl; sourceTree = "<group>"; };
>+		8350C3E71DA59B6200356434 /* ScrollOptions.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ScrollOptions.cpp; sourceTree = "<group>"; };
>+		8350C3E71DA59B6200356435 /* ScrollOptions.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ScrollOptions.h; sourceTree = "<group>"; };
>+		8350C3E81DA59B6200356435 /* ScrollOptions.idl */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = ScrollOptions.idl; sourceTree = "<group>"; };
> 		8350C3E71DA59B6200356446 /* ScrollToOptions.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ScrollToOptions.h; sourceTree = "<group>"; };
> 		8350C3E81DA59B6200356446 /* ScrollToOptions.idl */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = text; path = ScrollToOptions.idl; sourceTree = "<group>"; };
> 		83520C7D1A71BFCC006BD2AA /* CSSFontFamily.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = CSSFontFamily.h; sourceTree = "<group>"; };
>@@ -9907,6 +9916,10 @@
> 		83E8667D1FBA563F008855C5 /* ServiceWorkerData.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ServiceWorkerData.h; sourceTree = "<group>"; };
> 		83E8667F1FBA5640008855C5 /* ServiceWorkerData.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = ServiceWorkerData.cpp; sourceTree = "<group>"; };
> 		83E959E11B8BC22B004D9385 /* NativeNodeFilter.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = NativeNodeFilter.h; sourceTree = "<group>"; };
>+		83E9B3001DA5A51E00FFE8D4 /* JSScrollBehavior.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = JSScrollBehavior.cpp; sourceTree = "<group>"; };
>+		83E9B3011DA5A51E00FFE8D4 /* JSScrollBehavior.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = JSScrollBehavior.h; sourceTree = "<group>"; };
>+		83E9B3001DA5A51E00FFE8E5 /* JSScrollOptions.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = JSScrollOptions.cpp; sourceTree = "<group>"; };
>+		83E9B3011DA5A51E00FFE8E5 /* JSScrollOptions.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = JSScrollOptions.h; sourceTree = "<group>"; };
> 		83E9B3001DA5A51E00FFE8F6 /* JSScrollToOptions.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = JSScrollToOptions.cpp; sourceTree = "<group>"; };
> 		83E9B3011DA5A51E00FFE8F6 /* JSScrollToOptions.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = JSScrollToOptions.h; sourceTree = "<group>"; };
> 		83EE598B1F50958B003E8B30 /* JSErrorCallback.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = JSErrorCallback.h; sourceTree = "<group>"; };
>@@ -19360,6 +19373,11 @@
> 				BCEC01BA0C274DAC009F4EC9 /* Screen.cpp */,
> 				BCEC01BB0C274DAC009F4EC9 /* Screen.h */,
> 				BCEC01BC0C274DAC009F4EC9 /* Screen.idl */,
>+				8350C3E71DA59B6200356424 /* ScrollBehavior.h */,
>+				8350C3E81DA59B6200356424 /* ScrollBehavior.idl */,
>+				8350C3E71DA59B6200356434 /* ScrollOptions.cpp */,
>+				8350C3E71DA59B6200356435 /* ScrollOptions.h */,
>+				8350C3E81DA59B6200356435 /* ScrollOptions.idl */,
> 				8350C3E71DA59B6200356446 /* ScrollToOptions.h */,
> 				8350C3E81DA59B6200356446 /* ScrollToOptions.idl */,
> 				BCD0E0F70E972C3500265DEA /* SecurityOrigin.cpp */,
>@@ -24073,6 +24091,10 @@
> 				46C376612085176D00C73829 /* JSRemoteDOMWindow.h */,
> 				BCEC01C00C274DDD009F4EC9 /* JSScreen.cpp */,
> 				BCEC01C10C274DDD009F4EC9 /* JSScreen.h */,
>+				83E9B3001DA5A51E00FFE8D4 /* JSScrollBehavior.cpp */,
>+				83E9B3011DA5A51E00FFE8D4 /* JSScrollBehavior.h */,
>+				83E9B3001DA5A51E00FFE8E5 /* JSScrollOptions.cpp */,
>+				83E9B3011DA5A51E00FFE8E5 /* JSScrollOptions.h */,
> 				83E9B3001DA5A51E00FFE8F6 /* JSScrollToOptions.cpp */,
> 				83E9B3011DA5A51E00FFE8F6 /* JSScrollToOptions.h */,
> 				7C73FB0F191EF6F4007DE061 /* JSUserMessageHandler.cpp */,
>@@ -28849,6 +28871,8 @@
> 				5E2C436C1BCF071E0001E2BC /* JSRTCTrackEvent.h in Headers */,
> 				BCEC01C30C274DDD009F4EC9 /* JSScreen.h in Headers */,
> 				FDA15ECE12B03F61003A583A /* JSScriptProcessorNode.h in Headers */,
>+				834476EF1DA5BC5E002B6EB0 /* JSScrollBehavior.h in Headers */,
>+				834476EF1DA5BC5E002B6EC1 /* JSScrollOptions.h in Headers */,
> 				834476EF1DA5BC5E002B6ED2 /* JSScrollToOptions.h in Headers */,
> 				CED06AD11C77754800FDFAF1 /* JSSecurityPolicyViolationEvent.h in Headers */,
> 				5182C2561F3143CD0059BA7C /* JSServiceWorker.h in Headers */,
>@@ -30033,6 +30057,8 @@
> 				7AAFE8D019CB8672000F56D8 /* ScrollLatchingState.h in Headers */,
> 				F478755419983AFF0024A287 /* ScrollSnapAnimatorState.h in Headers */,
> 				F46729281E0DE68500ACC3D8 /* ScrollSnapOffsetsInfo.h in Headers */,
>+				83C5795D1DA5C301006FAC86 /* ScrollBehavior.h in Headers */,
>+				83C5795D1DA5C301006FAC97 /* ScrollOptions.h in Headers */,
> 				83C5795D1DA5C301006FACA8 /* ScrollToOptions.h in Headers */,
> 				93C09C860B0657AA005ABD4D /* ScrollTypes.h in Headers */,
> 				BC6D6E2609AF943500F59759 /* ScrollView.h in Headers */,
>diff --git a/Source/WebCore/css/CSSComputedStyleDeclaration.cpp b/Source/WebCore/css/CSSComputedStyleDeclaration.cpp
>index db9c6d79e08..b93a16c7206 100644
>--- a/Source/WebCore/css/CSSComputedStyleDeclaration.cpp
>+++ b/Source/WebCore/css/CSSComputedStyleDeclaration.cpp
>@@ -389,6 +389,9 @@ static const CSSPropertyID computedProperties[] = {
>     CSSPropertyOrder,
> #if ENABLE(ACCELERATED_OVERFLOW_SCROLLING)
>     CSSPropertyWebkitOverflowScrolling,
>+#endif
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    CSSPropertyScrollBehavior,
> #endif
>     CSSPropertyPerspective,
>     CSSPropertyPerspectiveOrigin,
>@@ -3681,6 +3684,12 @@ RefPtr<CSSValue> ComputedStyleExtractor::valueForPropertyinStyle(const RenderSty
>             if (!style.useTouchOverflowScrolling())
>                 return cssValuePool.createIdentifierValue(CSSValueAuto);
>             return cssValuePool.createIdentifierValue(CSSValueTouch);
>+#endif
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+        case CSSPropertyScrollBehavior:
>+            if (!style.useSmoothScrolling())
>+                return cssValuePool.createIdentifierValue(CSSValueAuto);
>+            return cssValuePool.createIdentifierValue(CSSValueSmooth);
> #endif
>         case CSSPropertyPerspective:
>             if (!style.hasPerspective())
>diff --git a/Source/WebCore/css/CSSProperties.json b/Source/WebCore/css/CSSProperties.json
>index 537dd70e58b..42fe8033eb7 100644
>--- a/Source/WebCore/css/CSSProperties.json
>+++ b/Source/WebCore/css/CSSProperties.json
>@@ -6211,6 +6211,23 @@
>                 "url": "https://www.w3.org/TR/css-ui-4/#propdef-user-select"
>             }
>         },
>+        "scroll-behavior": {
>+            "values": [
>+                "auto",
>+                "smooth"
>+            ],
>+            "codegen-properties": {
>+                "converter": "SmoothScrolling",
>+                "enable-if": "ENABLE_CSSOM_SMOOTH_SCROLLING",
>+                "name-for-methods": "UseSmoothScrolling"
>+            },
>+            "status": {
>+                "status": "in development"
>+            },
>+            "specification": {
>+                "url": "https://drafts.csswg.org/cssom-view/#propdef-scroll-behavior"
>+            }
>+        },
>         "scroll-padding": {
>             "codegen-properties": {
>                 "enable-if": "ENABLE_CSS_SCROLL_SNAP",
>diff --git a/Source/WebCore/css/CSSValueKeywords.in b/Source/WebCore/css/CSSValueKeywords.in
>index 74c450d09f6..c8471aeb236 100644
>--- a/Source/WebCore/css/CSSValueKeywords.in
>+++ b/Source/WebCore/css/CSSValueKeywords.in
>@@ -1356,6 +1356,11 @@ scroll-position
> manipulation
> #endif
> 
>+#if defined(ENABLE_CSSOM_SMOOTH_SCROLLING) && ENABLE_CSSOM_SMOOTH_SCROLLING
>+// scroll-behavior
>+smooth
>+#endif
>+
> // hanging-punctuation
> allow-end
> first
>diff --git a/Source/WebCore/css/StyleBuilderConverter.h b/Source/WebCore/css/StyleBuilderConverter.h
>index 60a24bc5141..470f92965fa 100644
>--- a/Source/WebCore/css/StyleBuilderConverter.h
>+++ b/Source/WebCore/css/StyleBuilderConverter.h
>@@ -114,6 +114,9 @@ public:
> #endif
> #if ENABLE(ACCELERATED_OVERFLOW_SCROLLING)
>     static bool convertOverflowScrolling(StyleResolver&, const CSSValue&);
>+#endif
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    static bool convertSmoothScrolling(StyleResolver&, const CSSValue&);
> #endif
>     static FontFeatureSettings convertFontFeatureSettings(StyleResolver&, const CSSValue&);
>     static FontSelectionValue convertFontWeightFromValue(const CSSValue&);
>@@ -1276,6 +1279,13 @@ inline bool StyleBuilderConverter::convertOverflowScrolling(StyleResolver&, cons
> }
> #endif
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+inline bool StyleBuilderConverter::convertSmoothScrolling(StyleResolver&, const CSSValue& value)
>+{
>+    return downcast<CSSPrimitiveValue>(value).valueID() == CSSValueSmooth;
>+}
>+#endif
>+
> inline SVGLengthValue StyleBuilderConverter::convertSVGLengthValue(StyleResolver&, const CSSValue& value)
> {
>     return SVGLengthValue::fromCSSPrimitiveValue(downcast<CSSPrimitiveValue>(value));
>diff --git a/Source/WebCore/css/parser/CSSParserFastPaths.cpp b/Source/WebCore/css/parser/CSSParserFastPaths.cpp
>index 87bc573cd58..ca7d50ddcda 100644
>--- a/Source/WebCore/css/parser/CSSParserFastPaths.cpp
>+++ b/Source/WebCore/css/parser/CSSParserFastPaths.cpp
>@@ -621,10 +621,10 @@ bool CSSParserFastPaths::isValidKeywordPropertyAndValue(CSSPropertyID propertyId
>         return valueID == CSSValueStatic || valueID == CSSValueRelative || valueID == CSSValueAbsolute || valueID == CSSValueFixed || valueID == CSSValueWebkitSticky;
>     case CSSPropertyResize: // none | both | horizontal | vertical | auto
>         return valueID == CSSValueNone || valueID == CSSValueBoth || valueID == CSSValueHorizontal || valueID == CSSValueVertical || valueID == CSSValueAuto;
>-    // FIXME-NEWPARSER: Investigate this property.
>-    // case CSSPropertyScrollBehavior: // auto | smooth
>-    //     ASSERT(RuntimeEnabledFeatures::cssomSmoothScrollEnabled());
>-    //   return valueID == CSSValueAuto || valueID == CSSValueSmooth;
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    case CSSPropertyScrollBehavior: // auto | smooth
>+        return valueID == CSSValueAuto || valueID == CSSValueSmooth;
>+#endif
>     case CSSPropertyShapeRendering:
>         return valueID == CSSValueAuto || valueID == CSSValueOptimizeSpeed || valueID == CSSValueCrispedges || valueID == CSSValueGeometricPrecision;
>     case CSSPropertyStrokeLinejoin:
>@@ -925,7 +925,9 @@ bool CSSParserFastPaths::isKeywordPropertyID(CSSPropertyID propertyId)
>     // case CSSPropertyFontKerning:
>     // case CSSPropertyHyphens:
>     // case CSSPropertyOverflowAnchor:
>-    // case CSSPropertyScrollBehavior:
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    case CSSPropertyScrollBehavior:
>+#endif
>     // case CSSPropertyScrollSnapType:
>     // case CSSPropertyTextAlignLast:
>     // case CSSPropertyTextCombineUpright:
>diff --git a/Source/WebCore/dom/Element.cpp b/Source/WebCore/dom/Element.cpp
>index b78da9cd332..02d0fd5abc7 100644
>--- a/Source/WebCore/dom/Element.cpp
>+++ b/Source/WebCore/dom/Element.cpp
>@@ -707,7 +707,7 @@ void Element::scrollBy(const ScrollToOptions& options)
> 
> void Element::scrollBy(double x, double y)
> {
>-    scrollBy({ x, y });
>+    scrollBy(fromCoordinates(x, y));
> }
> 
> void Element::scrollTo(const ScrollToOptions& options, ScrollClamping clamping)
>@@ -729,13 +729,24 @@ void Element::scrollTo(const ScrollToOptions& options, ScrollClamping clamping)
>         adjustForAbsoluteZoom(renderer->scrollLeft(), *renderer),
>         adjustForAbsoluteZoom(renderer->scrollTop(), *renderer)
>     );
>-    renderer->setScrollLeft(clampToInteger(scrollToOptions.left.value() * renderer->style().effectiveZoom()), clamping);
>-    renderer->setScrollTop(clampToInteger(scrollToOptions.top.value() * renderer->style().effectiveZoom()), clamping);
>+
>+    IntPoint scrollPosition(
>+        clampToInteger(scrollToOptions.left.value() * renderer->style().effectiveZoom()),
>+        clampToInteger(scrollToOptions.top.value() * renderer->style().effectiveZoom())
>+    );
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    if (scrollToOptions.useSmoothScrolling(this)) {
>+        renderer->scrollToPositionWithAnimation(scrollPosition, clamping);
>+        return;
>+    }
>+#endif
>+    renderer->setScrollLeft(scrollPosition.x(), clamping);
>+    renderer->setScrollTop(scrollPosition.y(), clamping);
> }
> 
> void Element::scrollTo(double x, double y)
> {
>-    scrollTo({ x, y });
>+    scrollTo(fromCoordinates(x, y));
> }
> 
> void Element::scrollByUnits(int units, ScrollGranularity granularity)
>diff --git a/Source/WebCore/page/DOMWindow.cpp b/Source/WebCore/page/DOMWindow.cpp
>index 57a3d8c03a9..65fff12cf58 100644
>--- a/Source/WebCore/page/DOMWindow.cpp
>+++ b/Source/WebCore/page/DOMWindow.cpp
>@@ -1574,7 +1574,7 @@ double DOMWindow::devicePixelRatio() const
> 
> void DOMWindow::scrollBy(double x, double y) const
> {
>-    scrollBy({ x, y });
>+    return scrollBy(fromCoordinates(x, y));
> }
> 
> void DOMWindow::scrollBy(const ScrollToOptions& options) const
>@@ -1596,10 +1596,10 @@ void DOMWindow::scrollBy(const ScrollToOptions& options) const
> 
> void DOMWindow::scrollTo(double x, double y, ScrollClamping clamping) const
> {
>-    scrollTo({ x, y }, clamping);
>+    return scrollTo(fromCoordinates(x, y), clamping);
> }
> 
>-void DOMWindow::scrollTo(const ScrollToOptions& options, ScrollClamping) const
>+void DOMWindow::scrollTo(const ScrollToOptions& options, ScrollClamping clamping) const
> {
>     if (!isCurrentlyDisplayedInFrame())
>         return;
>@@ -1618,6 +1618,14 @@ void DOMWindow::scrollTo(const ScrollToOptions& options, ScrollClamping) const
>     document()->updateLayoutIgnorePendingStylesheets();
> 
>     IntPoint layoutPos(view->mapFromCSSToLayoutUnits(scrollToOptions.left.value()), view->mapFromCSSToLayoutUnits(scrollToOptions.top.value()));
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    // FIXME: Should we use document()->scrollingElement()?
>+    // See https://github.com/w3c/csswg-drafts/issues/2977
>+    if (scrollToOptions.useSmoothScrolling(document()->documentElement())) {
>+        view->scrollToOffsetWithAnimation(layoutPos, clamping);
>+        return;
>+    }
>+#endif
>     view->setContentsScrollPosition(layoutPos);
> }
> 
>diff --git a/Source/WebCore/page/ScrollBehavior.h b/Source/WebCore/page/ScrollBehavior.h
>new file mode 100644
>index 00000000000..c875dcd5f79
>--- /dev/null
>+++ b/Source/WebCore/page/ScrollBehavior.h
>@@ -0,0 +1,34 @@
>+/*
>+ * Copyright (C) 2018 Igalia S.L.
>+ *
>+ * This library is free software; you can redistribute it and/or
>+ * modify it under the terms of the GNU Library General Public
>+ * License as published by the Free Software Foundation; either
>+ * version 2 of the License, or (at your option) any later version.
>+ *
>+ * This library is distributed in the hope that it will be useful,
>+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
>+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>+ * Library General Public License for more details.
>+ *
>+ * You should have received a copy of the GNU Library General Public License
>+ * along with this library; see the file COPYING.LIB.  If not, write to
>+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
>+ * Boston, MA 02110-1301, USA.
>+ */
>+
>+#pragma once
>+
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+
>+namespace WebCore {
>+
>+enum class ScrollBehavior {
>+    Auto = 0,
>+    Instant,
>+    Smooth
>+};
>+
>+#endif // ENABLE(CSSOM_SMOOTH_SCROLLING)
>+
>+}
>diff --git a/Source/WebCore/page/ScrollBehavior.idl b/Source/WebCore/page/ScrollBehavior.idl
>new file mode 100644
>index 00000000000..a865fbe665b
>--- /dev/null
>+++ b/Source/WebCore/page/ScrollBehavior.idl
>@@ -0,0 +1,20 @@
>+/*
>+ * Copyright (C) 2018 Igalia S.L.
>+ *
>+ * This library is free software; you can redistribute it and/or
>+ * modify it under the terms of the GNU Library General Public
>+ * License as published by the Free Software Foundation; either
>+ * version 2 of the License, or (at your option) any later version.
>+ *
>+ * This library is distributed in the hope that it will be useful,
>+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
>+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>+ * Library General Public License for more details.
>+ *
>+ * You should have received a copy of the GNU Library General Public License
>+ * along with this library; see the file COPYING.LIB.  If not, write to
>+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
>+ * Boston, MA 02110-1301, USA.
>+ */
>+
>+enum ScrollBehavior { "auto", "instant", "smooth" };
>diff --git a/Source/WebCore/page/ScrollOptions.cpp b/Source/WebCore/page/ScrollOptions.cpp
>new file mode 100644
>index 00000000000..a34c38587d6
>--- /dev/null
>+++ b/Source/WebCore/page/ScrollOptions.cpp
>@@ -0,0 +1,52 @@
>+/*
>+ * Copyright (C) 2018 Igalia S.L.
>+ *
>+ * This library is free software; you can redistribute it and/or
>+ * modify it under the terms of the GNU Library General Public
>+ * License as published by the Free Software Foundation; either
>+ * version 2 of the License, or (at your option) any later version.
>+ *
>+ * This library is distributed in the hope that it will be useful,
>+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
>+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>+ * Library General Public License for more details.
>+ *
>+ * You should have received a copy of the GNU Library General Public License
>+ * along with this library; see the file COPYING.LIB.  If not, write to
>+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
>+ * Boston, MA 02110-1301, USA.
>+ */
>+
>+#include "config.h"
>+#include "ScrollOptions.h"
>+
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+
>+#include "Element.h"
>+#include "RenderElement.h"
>+#include "RenderStyle.h"
>+#include "Settings.h"
>+
>+namespace WebCore {
>+
>+bool ScrollOptions::useSmoothScrolling(Element* associatedElement) const
>+{
>+    if (!associatedElement || !associatedElement->document().settings().cssomSmoothScrollingEnabled() || !associatedElement->renderer())
>+        return false;
>+
>+    // https://drafts.csswg.org/cssom-view/#scrolling
>+    switch (behavior.value_or(ScrollBehavior::Auto)) {
>+    case ScrollBehavior::Auto:
>+        return associatedElement->renderer()->style().useSmoothScrolling();
>+    case ScrollBehavior::Instant:
>+        return false;
>+    case ScrollBehavior::Smooth:
>+        return true;
>+    }
>+    ASSERT_NOT_REACHED();
>+    return false;
>+}
>+
>+} // namespace WebCore
>+
>+#endif // ENABLE(CSSOM_SMOOTH_SCROLLING)
>diff --git a/Source/WebCore/page/ScrollOptions.h b/Source/WebCore/page/ScrollOptions.h
>new file mode 100644
>index 00000000000..1d9b9b5555d
>--- /dev/null
>+++ b/Source/WebCore/page/ScrollOptions.h
>@@ -0,0 +1,37 @@
>+/*
>+ * Copyright (C) 2018 Igalia S.L.
>+ *
>+ * This library is free software; you can redistribute it and/or
>+ * modify it under the terms of the GNU Library General Public
>+ * License as published by the Free Software Foundation; either
>+ * version 2 of the License, or (at your option) any later version.
>+ *
>+ * This library is distributed in the hope that it will be useful,
>+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
>+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>+ * Library General Public License for more details.
>+ *
>+ * You should have received a copy of the GNU Library General Public License
>+ * along with this library; see the file COPYING.LIB.  If not, write to
>+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
>+ * Boston, MA 02110-1301, USA.
>+ */
>+
>+#pragma once
>+
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+
>+#include "ScrollBehavior.h"
>+
>+namespace WebCore {
>+
>+class Element;
>+
>+struct ScrollOptions {
>+    std::optional<ScrollBehavior> behavior { ScrollBehavior::Auto };
>+    bool useSmoothScrolling(Element*) const;
>+};
>+
>+} // namespace WebCore
>+
>+#endif // ENABLE(CSSOM_SMOOTH_SCROLLING)
>diff --git a/Source/WebCore/page/ScrollOptions.idl b/Source/WebCore/page/ScrollOptions.idl
>new file mode 100644
>index 00000000000..140f5c70ed1
>--- /dev/null
>+++ b/Source/WebCore/page/ScrollOptions.idl
>@@ -0,0 +1,22 @@
>+/*
>+ * Copyright (C) 2018 Igalia S.L.
>+ *
>+ * This library is free software; you can redistribute it and/or
>+ * modify it under the terms of the GNU Library General Public
>+ * License as published by the Free Software Foundation; either
>+ * version 2 of the License, or (at your option) any later version.
>+ *
>+ * This library is distributed in the hope that it will be useful,
>+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
>+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
>+ * Library General Public License for more details.
>+ *
>+ * You should have received a copy of the GNU Library General Public License
>+ * along with this library; see the file COPYING.LIB.  If not, write to
>+ * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
>+ * Boston, MA 02110-1301, USA.
>+ */
>+
>+dictionary ScrollOptions {
>+    ScrollBehavior behavior = "auto";
>+};
>diff --git a/Source/WebCore/page/ScrollToOptions.h b/Source/WebCore/page/ScrollToOptions.h
>index 87eeaa9cca9..1fe91f607d7 100644
>--- a/Source/WebCore/page/ScrollToOptions.h
>+++ b/Source/WebCore/page/ScrollToOptions.h
>@@ -31,13 +31,29 @@
> #include <cmath>
> #include <wtf/Optional.h>
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+#include "ScrollOptions.h"
>+#endif
>+
> namespace WebCore {
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+struct ScrollToOptions : ScrollOptions {
>+#else
> struct ScrollToOptions {
>+#endif
>     std::optional<double> left;
>     std::optional<double> top;
> };
> 
>+inline ScrollToOptions fromCoordinates(double x, double y)
>+{
>+    ScrollToOptions options;
>+    options.left = x;
>+    options.top = y;
>+    return options;
>+};
>+
> inline double normalizeNonFiniteValueOrFallBackTo(std::optional<double> value, double fallbackValue)
> {
>     // Normalize non-finite values (https://drafts.csswg.org/cssom-view/#normalize-non-finite-values).
>@@ -47,7 +63,7 @@ inline double normalizeNonFiniteValueOrFallBackTo(std::optional<double> value, d
> // FIXME(https://webkit.org/b/88339): Consider using FloatPoint or DoublePoint for fallback and return values.
> inline ScrollToOptions normalizeNonFiniteCoordinatesOrFallBackTo(const ScrollToOptions& value, double x, double y)
> {
>-    ScrollToOptions options;
>+    ScrollToOptions options = value;
>     options.left = normalizeNonFiniteValueOrFallBackTo(value.left, x);
>     options.top = normalizeNonFiniteValueOrFallBackTo(value.top, y);
>     return options;
>diff --git a/Source/WebCore/page/ScrollToOptions.idl b/Source/WebCore/page/ScrollToOptions.idl
>index 510bc071a68..d66c20edcb1 100644
>--- a/Source/WebCore/page/ScrollToOptions.idl
>+++ b/Source/WebCore/page/ScrollToOptions.idl
>@@ -26,8 +26,11 @@
>  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
>  */
> 
>-// FIXME(webkit.org/b/188043): Support ScrollBehavior.
>+#if defined(ENABLE_CSSOM_SMOOTH_SCROLLING) && ENABLE_CSSOM_SMOOTH_SCROLLING
>+dictionary ScrollToOptions : ScrollOptions {
>+#else
> dictionary ScrollToOptions {
>+#endif
>     unrestricted double left;
>     unrestricted double top;
> };
>diff --git a/Source/WebCore/page/Settings.yaml b/Source/WebCore/page/Settings.yaml
>index 2122e909135..82c42286eb6 100644
>--- a/Source/WebCore/page/Settings.yaml
>+++ b/Source/WebCore/page/Settings.yaml
>@@ -364,6 +364,9 @@ frameFlattening:
> asyncFrameScrollingEnabled:
>   initial: false
>   onChange: setNeedsRelayoutAllFrames
>+cssomSmoothScrollingEnabled:
>+  type: bool
>+  initial: false
> 
> webSecurityEnabled:
>   initial: true
>diff --git a/Source/WebCore/platform/ScrollAnimation.h b/Source/WebCore/platform/ScrollAnimation.h
>index 2e5f63bcef2..45b7c260443 100644
>--- a/Source/WebCore/platform/ScrollAnimation.h
>+++ b/Source/WebCore/platform/ScrollAnimation.h
>@@ -32,11 +32,13 @@ namespace WebCore {
> 
> class FloatPoint;
> class ScrollableArea;
>+enum class ScrollClamping;
> 
> class ScrollAnimation {
> public:
>     virtual ~ScrollAnimation() { };
>     virtual bool scroll(ScrollbarOrientation, ScrollGranularity, float /* step */, float /* multiplier */) { return true; };
>+    virtual bool scroll(const FloatPoint&, ScrollClamping) { return true; };
>     virtual void stop() = 0;
>     virtual void updateVisibleLengths() { };
>     virtual void setCurrentPosition(const FloatPoint&) { };
>diff --git a/Source/WebCore/platform/ScrollAnimationSmooth.cpp b/Source/WebCore/platform/ScrollAnimationSmooth.cpp
>index d064e69379f..c9882f30f96 100644
>--- a/Source/WebCore/platform/ScrollAnimationSmooth.cpp
>+++ b/Source/WebCore/platform/ScrollAnimationSmooth.cpp
>@@ -28,7 +28,7 @@
> #include "config.h"
> #include "ScrollAnimationSmooth.h"
> 
>-#if ENABLE(SMOOTH_SCROLLING)
>+#if ENABLE(SMOOTH_SCROLLING) || ENABLE(CSSOM_SMOOTH_SCROLLING)
> 
> #include "FloatPoint.h"
> #include "ScrollableArea.h"
>@@ -67,6 +67,22 @@ bool ScrollAnimationSmooth::scroll(ScrollbarOrientation orientation, ScrollGranu
>     return needToScroll;
> }
> 
>+bool ScrollAnimationSmooth::scroll(const FloatPoint& position, ScrollClamping)
>+{
>+    // FIXME: clamping?
>+    bool needToScroll = updatePerAxisData(m_horizontalData, ScrollByPixel, position.x(), m_scrollableArea.minimumScrollPosition().x(), m_scrollableArea.maximumScrollPosition().x());
>+    m_verticalData.startTime = m_horizontalData.startTime;
>+    needToScroll |=
>+        updatePerAxisData(m_verticalData, ScrollByPixel, position.y(), m_scrollableArea.minimumScrollPosition().y(), m_scrollableArea.maximumScrollPosition().y());
>+    // FIXME: cancel active scroll?
>+    // FIXME: bidirectional scrolling does not work.
>+    if (needToScroll && !animationTimerActive()) {
>+        m_startTime = m_horizontalData.startTime;
>+        animationTimerFired();
>+    }
>+    return needToScroll;
>+};
>+
> void ScrollAnimationSmooth::stop()
> {
>     m_animationTimer.stop();
>@@ -408,4 +424,4 @@ bool ScrollAnimationSmooth::animationTimerActive() const
> 
> } // namespace WebCore
> 
>-#endif // ENABLE(SMOOTH_SCROLLING)
>+#endif // ENABLE(SMOOTH_SCROLLING) || ENABLE(CSSOM_SMOOTH_SCROLLING)
>diff --git a/Source/WebCore/platform/ScrollAnimationSmooth.h b/Source/WebCore/platform/ScrollAnimationSmooth.h
>index 02cc4ee2bd7..c97f889a241 100644
>--- a/Source/WebCore/platform/ScrollAnimationSmooth.h
>+++ b/Source/WebCore/platform/ScrollAnimationSmooth.h
>@@ -27,7 +27,7 @@
> 
> #include "ScrollAnimation.h"
> 
>-#if ENABLE(SMOOTH_SCROLLING)
>+#if ENABLE(SMOOTH_SCROLLING) || ENABLE(CSSOM_SMOOTH_SCROLLING)
> 
> #include "Timer.h"
> 
>@@ -35,6 +35,7 @@ namespace WebCore {
> 
> class FloatPoint;
> class ScrollableArea;
>+enum class ScrollClamping;
> 
> class ScrollAnimationSmooth final: public ScrollAnimation {
> public:
>@@ -51,6 +52,7 @@ public:
> 
> private:
>     bool scroll(ScrollbarOrientation, ScrollGranularity, float step, float multiplier) override;
>+    bool scroll(const FloatPoint&, ScrollClamping) override;
>     void stop() override;
>     void updateVisibleLengths() override;
>     void setCurrentPosition(const FloatPoint&) override;
>@@ -108,4 +110,4 @@ private:
> 
> } // namespace WebCore
> 
>-#endif // ENABLE(SMOOTH_SCROLLING)
>+#endif // ENABLE(SMOOTH_SCROLLING) || ENABLE(CSSOM_SMOOTH_SCROLLING)
>diff --git a/Source/WebCore/platform/ScrollAnimator.cpp b/Source/WebCore/platform/ScrollAnimator.cpp
>index 0db3408ab16..38eafc97855 100644
>--- a/Source/WebCore/platform/ScrollAnimator.cpp
>+++ b/Source/WebCore/platform/ScrollAnimator.cpp
>@@ -38,6 +38,10 @@
> #include "ScrollableArea.h"
> #include <algorithm>
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+#include "ScrollAnimationSmooth.h"
>+#endif
>+
> namespace WebCore {
> 
> #if !ENABLE(SMOOTH_SCROLLING) && !PLATFORM(IOS) && !PLATFORM(MAC)
>@@ -52,6 +56,13 @@ ScrollAnimator::ScrollAnimator(ScrollableArea& scrollableArea)
> #if ENABLE(CSS_SCROLL_SNAP) || ENABLE(RUBBER_BANDING)
>     , m_scrollController(*this)
> #endif
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    , m_animationProgrammaticScroll(std::make_unique<ScrollAnimationSmooth>(scrollableArea, m_currentPosition, [this](FloatPoint&& position) {
>+        FloatSize delta = position - m_currentPosition;
>+        m_currentPosition = WTFMove(position);
>+        notifyPositionChanged(delta);
>+    }))
>+#endif
> {
> }
> 
>@@ -75,6 +86,14 @@ bool ScrollAnimator::scroll(ScrollbarOrientation orientation, ScrollGranularity,
>     return true;
> }
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+void ScrollAnimator::scrollToOffset(const FloatPoint& offset, ScrollClamping clamping)
>+{
>+    auto newPosition = ScrollableArea::scrollPositionFromOffset(offset, toFloatSize(m_scrollableArea.scrollOrigin()));
>+    m_animationProgrammaticScroll->scroll(newPosition, clamping);
>+}
>+#endif
>+
> void ScrollAnimator::scrollToOffsetWithoutAnimation(const FloatPoint& offset, ScrollClamping)
> {
>     FloatPoint newPositon = ScrollableArea::scrollPositionFromOffset(offset, toFloatSize(m_scrollableArea.scrollOrigin()));
>@@ -245,4 +264,39 @@ void ScrollAnimator::removeTestDeferralForReason(WheelEventTestTrigger::Scrollab
> }
> #endif
> 
>+void ScrollAnimator::cancelAnimations()
>+{
>+#if !USE(REQUEST_ANIMATION_FRAME_TIMER)
>+    m_animationProgrammaticScroll->stop();
>+#endif
>+}
>+
>+void ScrollAnimator::serviceScrollAnimations()
>+{
>+#if !USE(REQUEST_ANIMATION_FRAME_TIMER)
>+    m_animationProgrammaticScroll->serviceAnimation();
>+#endif
>+}
>+
>+void ScrollAnimator::willEndLiveResize()
>+{
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    m_animationProgrammaticScroll->updateVisibleLengths();
>+#endif
>+}
>+
>+void ScrollAnimator::didAddVerticalScrollbar(Scrollbar*)
>+{
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    m_animationProgrammaticScroll->updateVisibleLengths();
>+#endif
>+}
>+
>+void ScrollAnimator::didAddHorizontalScrollbar(Scrollbar*)
>+{
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    m_animationProgrammaticScroll->updateVisibleLengths();
>+#endif
>+}
>+
> } // namespace WebCore
>diff --git a/Source/WebCore/platform/ScrollAnimator.h b/Source/WebCore/platform/ScrollAnimator.h
>index 6e2a884abb2..d749783fb68 100644
>--- a/Source/WebCore/platform/ScrollAnimator.h
>+++ b/Source/WebCore/platform/ScrollAnimator.h
>@@ -50,6 +50,10 @@ class ScrollableArea;
> class Scrollbar;
> class WheelEventTestTrigger;
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+class ScrollAnimation;
>+#endif
>+
> #if ENABLE(CSS_SCROLL_SNAP) || ENABLE(RUBBER_BANDING)
> class ScrollAnimator : private ScrollControllerClient {
> #else
>@@ -68,6 +72,9 @@ public:
>     // The base class implementation always scrolls immediately, never animates.
>     virtual bool scroll(ScrollbarOrientation, ScrollGranularity, float step, float multiplier);
> 
>+#if ENABLE_CSSOM_SMOOTH_SCROLLING
>+    void scrollToOffset(const FloatPoint&, ScrollClamping = ScrollClamping::Clamped);
>+#endif
>     virtual void scrollToOffsetWithoutAnimation(const FloatPoint&, ScrollClamping = ScrollClamping::Clamped);
> 
>     ScrollableArea& scrollableArea() const { return m_scrollableArea; }
>@@ -85,8 +92,8 @@ public:
>     void setCurrentPosition(const FloatPoint&);
>     const FloatPoint& currentPosition() const { return m_currentPosition; }
> 
>-    virtual void cancelAnimations() { }
>-    virtual void serviceScrollAnimations() { }
>+    virtual void cancelAnimations();
>+    virtual void serviceScrollAnimations();
> 
>     virtual void contentAreaWillPaint() const { }
>     virtual void mouseEnteredContentArea() { }
>@@ -97,16 +104,16 @@ public:
>     virtual void mouseIsDownInScrollbar(Scrollbar*, bool) const { }
>     virtual void willStartLiveResize() { }
>     virtual void contentsResized() const { }
>-    virtual void willEndLiveResize() { }
>+    virtual void willEndLiveResize();
>     virtual void contentAreaDidShow() { }
>     virtual void contentAreaDidHide() { }
> 
>     virtual void lockOverlayScrollbarStateToHidden(bool) { }
>     virtual bool scrollbarsCanBeActive() const { return true; }
> 
>-    virtual void didAddVerticalScrollbar(Scrollbar*) { }
>+    virtual void didAddVerticalScrollbar(Scrollbar*);
>     virtual void willRemoveVerticalScrollbar(Scrollbar*) { }
>-    virtual void didAddHorizontalScrollbar(Scrollbar*) { }
>+    virtual void didAddHorizontalScrollbar(Scrollbar*);
>     virtual void willRemoveHorizontalScrollbar(Scrollbar*) { }
> 
>     virtual void invalidateScrollbarPartLayers(Scrollbar*) { }
>@@ -150,6 +157,10 @@ protected:
>     ScrollController m_scrollController;
> #endif
>     FloatPoint m_currentPosition;
>+
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    std::unique_ptr<ScrollAnimation> m_animationProgrammaticScroll;
>+#endif
> };
> 
> } // namespace WebCore
>diff --git a/Source/WebCore/platform/ScrollAnimatorSmooth.cpp b/Source/WebCore/platform/ScrollAnimatorSmooth.cpp
>index defc3f1978f..19b6edb6bb5 100644
>--- a/Source/WebCore/platform/ScrollAnimatorSmooth.cpp
>+++ b/Source/WebCore/platform/ScrollAnimatorSmooth.cpp
>@@ -79,27 +79,32 @@ void ScrollAnimatorSmooth::scrollToOffsetWithoutAnimation(const FloatPoint& offs
> #if !USE(REQUEST_ANIMATION_FRAME_TIMER)
> void ScrollAnimatorSmooth::cancelAnimations()
> {
>+    ScrollAnimator::cancelAnimations();
>     m_animation->stop();
> }
> 
> void ScrollAnimatorSmooth::serviceScrollAnimations()
> {
>+    ScrollAnimator::serviceScrollAnimations();
>     m_animation->serviceAnimation();
> }
> #endif
> 
> void ScrollAnimatorSmooth::willEndLiveResize()
> {
>+    ScrollAnimator::willEndLiveResize();
>     m_animation->updateVisibleLengths();
> }
> 
>-void ScrollAnimatorSmooth::didAddVerticalScrollbar(Scrollbar*)
>+void ScrollAnimatorSmooth::didAddVerticalScrollbar(Scrollbar* scrollbar)
> {
>+    ScrollAnimator::didAddVerticalScrollbar(scrollbar);
>     m_animation->updateVisibleLengths();
> }
> 
>-void ScrollAnimatorSmooth::didAddHorizontalScrollbar(Scrollbar*)
>+void ScrollAnimatorSmooth::didAddHorizontalScrollbar(Scrollbar* scrollbar)
> {
>+    ScrollAnimator::didAddHorizontalScrollbar(scrollbar);
>     m_animation->updateVisibleLengths();
> }
> 
>diff --git a/Source/WebCore/platform/ScrollableArea.cpp b/Source/WebCore/platform/ScrollableArea.cpp
>index 7b1d359dbc6..ea751ff16d9 100644
>--- a/Source/WebCore/platform/ScrollableArea.cpp
>+++ b/Source/WebCore/platform/ScrollableArea.cpp
>@@ -138,6 +138,14 @@ bool ScrollableArea::scroll(ScrollDirection direction, ScrollGranularity granula
>     return scrollAnimator().scroll(orientation, granularity, step, multiplier);
> }
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+void ScrollableArea::scrollToOffsetWithAnimation(const FloatPoint& offset, ScrollClamping clamping)
>+{
>+    LOG_WITH_STREAM(Scrolling, stream << "ScrollableArea " << this << " scrollToOffset " << offset);
>+    scrollAnimator().scrollToOffset(offset, clamping);
>+}
>+#endif
>+
> void ScrollableArea::scrollToOffsetWithoutAnimation(const FloatPoint& offset, ScrollClamping clamping)
> {
>     LOG_WITH_STREAM(Scrolling, stream << "ScrollableArea " << this << " scrollToOffsetWithoutAnimation " << offset);
>diff --git a/Source/WebCore/platform/ScrollableArea.h b/Source/WebCore/platform/ScrollableArea.h
>index 068b3bc7435..3a5c5cc9516 100644
>--- a/Source/WebCore/platform/ScrollableArea.h
>+++ b/Source/WebCore/platform/ScrollableArea.h
>@@ -51,6 +51,9 @@ typedef IntPoint ScrollOffset;
> class ScrollableArea : public CanMakeWeakPtr<ScrollableArea> {
> public:
>     WEBCORE_EXPORT bool scroll(ScrollDirection, ScrollGranularity, float multiplier = 1);
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    WEBCORE_EXPORT void scrollToOffsetWithAnimation(const FloatPoint&, ScrollClamping = ScrollClamping::Clamped);
>+#endif
>     WEBCORE_EXPORT void scrollToOffsetWithoutAnimation(const FloatPoint&, ScrollClamping = ScrollClamping::Clamped);
>     void scrollToOffsetWithoutAnimation(ScrollbarOrientation, float offset);
> 
>diff --git a/Source/WebCore/rendering/RenderBox.cpp b/Source/WebCore/rendering/RenderBox.cpp
>index 5a2ef2f3758..24fe3ca0594 100644
>--- a/Source/WebCore/rendering/RenderBox.cpp
>+++ b/Source/WebCore/rendering/RenderBox.cpp
>@@ -586,6 +586,14 @@ void RenderBox::setScrollTop(int newTop, ScrollClamping clamping)
>     layer()->scrollToYPosition(newTop, clamping);
> }
> 
>+void RenderBox::scrollToPositionWithAnimation(ScrollPosition scrollPosition, ScrollClamping clamping)
>+{
>+    if (!hasOverflowClip() || !layer())
>+        return;
>+    setupWheelEventTestTrigger(*layer());
>+    layer()->scrollToOffsetWithAnimation(scrollPosition, clamping);
>+}
>+
> void RenderBox::absoluteRects(Vector<IntRect>& rects, const LayoutPoint& accumulatedOffset) const
> {
>     rects.append(snappedIntRect(accumulatedOffset, size()));
>diff --git a/Source/WebCore/rendering/RenderBox.h b/Source/WebCore/rendering/RenderBox.h
>index 81663f74d2b..d0cc0e77360 100644
>--- a/Source/WebCore/rendering/RenderBox.h
>+++ b/Source/WebCore/rendering/RenderBox.h
>@@ -245,6 +245,7 @@ public:
>     virtual int scrollHeight() const;
>     virtual void setScrollLeft(int, ScrollClamping = ScrollClamping::Clamped);
>     virtual void setScrollTop(int, ScrollClamping = ScrollClamping::Clamped);
>+    void scrollToPositionWithAnimation(ScrollPosition, ScrollClamping = ScrollClamping::Clamped);
> 
>     LayoutUnit marginTop() const override { return m_marginBox.top(); }
>     LayoutUnit marginBottom() const override { return m_marginBox.bottom(); }
>diff --git a/Source/WebCore/rendering/RenderLayer.cpp b/Source/WebCore/rendering/RenderLayer.cpp
>index 0678dee81bf..caef962ebe9 100644
>--- a/Source/WebCore/rendering/RenderLayer.cpp
>+++ b/Source/WebCore/rendering/RenderLayer.cpp
>@@ -2372,6 +2372,15 @@ void RenderLayer::scrollToOffset(const ScrollOffset& scrollOffset, ScrollClampin
>         scrollToOffsetWithoutAnimation(newScrollOffset, clamping);
> }
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+void RenderLayer::scrollToOffsetWithAnimation(const ScrollOffset& scrollOffset, ScrollClamping clamping)
>+{
>+    ScrollOffset newScrollOffset = clamping == ScrollClamping::Clamped ? clampScrollOffset(scrollOffset) : scrollOffset;
>+    if (newScrollOffset != this->scrollOffset())
>+        ScrollableArea::scrollToOffsetWithAnimation(newScrollOffset, clamping);
>+}
>+#endif
>+
> void RenderLayer::scrollTo(const ScrollPosition& position)
> {
>     RenderBox* box = renderBox();
>diff --git a/Source/WebCore/rendering/RenderLayer.h b/Source/WebCore/rendering/RenderLayer.h
>index d6fe3df1bcb..89ced9ff88b 100644
>--- a/Source/WebCore/rendering/RenderLayer.h
>+++ b/Source/WebCore/rendering/RenderLayer.h
>@@ -203,6 +203,9 @@ public:
>     void scrollByRecursively(const IntSize& delta, ScrollableArea** scrolledArea = nullptr);
> 
>     WEBCORE_EXPORT void scrollToOffset(const ScrollOffset&, ScrollClamping = ScrollClamping::Clamped);
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    WEBCORE_EXPORT void scrollToOffsetWithAnimation(const ScrollOffset&, ScrollClamping = ScrollClamping::Clamped);
>+#endif
>     void scrollToXOffset(int x, ScrollClamping clamping = ScrollClamping::Clamped) { scrollToOffset(ScrollOffset(x, scrollOffset().y()), clamping); }
>     void scrollToYOffset(int y, ScrollClamping clamping = ScrollClamping::Clamped) { scrollToOffset(ScrollOffset(scrollOffset().x(), y), clamping); }
> 
>diff --git a/Source/WebCore/rendering/style/RenderStyle.h b/Source/WebCore/rendering/style/RenderStyle.h
>index 42c8b452c60..b9bbfff12a8 100644
>--- a/Source/WebCore/rendering/style/RenderStyle.h
>+++ b/Source/WebCore/rendering/style/RenderStyle.h
>@@ -723,6 +723,10 @@ public:
>     bool useTouchOverflowScrolling() const { return m_rareInheritedData->useTouchOverflowScrolling; }
> #endif
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    bool useSmoothScrolling() const { return m_rareNonInheritedData->useSmoothScrolling; }
>+#endif
>+
> #if ENABLE(TEXT_AUTOSIZING)
>     TextSizeAdjustment textSizeAdjust() const { return m_rareInheritedData->textSizeAdjust; }
> #endif
>@@ -1232,6 +1236,10 @@ public:
>     void setUseTouchOverflowScrolling(bool v) { SET_VAR(m_rareInheritedData, useTouchOverflowScrolling, v); }
> #endif
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    void setUseSmoothScrolling(bool v) { SET_VAR(m_rareNonInheritedData, useSmoothScrolling, v); }
>+#endif
>+
> #if ENABLE(TEXT_AUTOSIZING)
>     void setTextSizeAdjust(TextSizeAdjustment adjustment) { SET_VAR(m_rareInheritedData, textSizeAdjust, adjustment); }
> #endif
>@@ -1658,6 +1666,10 @@ public:
>     static bool initialUseTouchOverflowScrolling() { return false; }
> #endif
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    static bool initialUseSmoothScrolling() { return false; }
>+#endif
>+
> #if ENABLE(DASHBOARD_SUPPORT)
>     static const Vector<StyleDashboardRegion>& initialDashboardRegions();
>     static const Vector<StyleDashboardRegion>& noneDashboardRegions();
>diff --git a/Source/WebCore/rendering/style/StyleRareNonInheritedData.cpp b/Source/WebCore/rendering/style/StyleRareNonInheritedData.cpp
>index 0aeac9750c6..acd4dcf3694 100644
>--- a/Source/WebCore/rendering/style/StyleRareNonInheritedData.cpp
>+++ b/Source/WebCore/rendering/style/StyleRareNonInheritedData.cpp
>@@ -77,6 +77,9 @@ StyleRareNonInheritedData::StyleRareNonInheritedData()
>     , justifySelf(RenderStyle::initialSelfAlignment())
> #if ENABLE(TOUCH_EVENTS)
>     , touchAction(static_cast<unsigned>(RenderStyle::initialTouchAction()))
>+#endif
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    , useSmoothScrolling(static_cast<unsigned>(RenderStyle::initialUseSmoothScrolling()))
> #endif
>     , pageSizeType(PAGE_SIZE_AUTO)
>     , transformStyle3D(static_cast<unsigned>(RenderStyle::initialTransformStyle3D()))
>@@ -169,6 +172,9 @@ inline StyleRareNonInheritedData::StyleRareNonInheritedData(const StyleRareNonIn
>     , justifySelf(o.justifySelf)
> #if ENABLE(TOUCH_EVENTS)
>     , touchAction(o.touchAction)
>+#endif
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    , useSmoothScrolling(o.useSmoothScrolling)
> #endif
>     , pageSizeType(o.pageSizeType)
>     , transformStyle3D(o.transformStyle3D)
>@@ -282,6 +288,9 @@ bool StyleRareNonInheritedData::operator==(const StyleRareNonInheritedData& o) c
> #if ENABLE(TOUCH_EVENTS)
>         && touchAction == o.touchAction
> #endif
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+        && useSmoothScrolling == o.useSmoothScrolling
>+#endif
> #if ENABLE(CSS_COMPOSITING)
>         && effectiveBlendMode == o.effectiveBlendMode
>         && isolation == o.isolation
>diff --git a/Source/WebCore/rendering/style/StyleRareNonInheritedData.h b/Source/WebCore/rendering/style/StyleRareNonInheritedData.h
>index 089ccfa438c..1bd01518e70 100644
>--- a/Source/WebCore/rendering/style/StyleRareNonInheritedData.h
>+++ b/Source/WebCore/rendering/style/StyleRareNonInheritedData.h
>@@ -175,6 +175,10 @@ public:
>     unsigned touchAction : 1; // TouchAction
> #endif
> 
>+#if ENABLE(CSSOM_SMOOTH_SCROLLING)
>+    unsigned useSmoothScrolling : 1; // ScrollBehavior
>+#endif
>+
>     unsigned pageSizeType : 2; // PageSizeType
>     unsigned transformStyle3D : 1; // TransformStyle3D
>     unsigned backfaceVisibility : 1; // BackfaceVisibility
>diff --git a/Source/WebCore/testing/Internals.cpp b/Source/WebCore/testing/Internals.cpp
>index c600b35b296..d62a6f8bb8d 100644
>--- a/Source/WebCore/testing/Internals.cpp
>+++ b/Source/WebCore/testing/Internals.cpp
>@@ -1625,7 +1625,7 @@ ExceptionOr<void> Internals::unconstrainedScrollTo(Element& element, double x, d
>     if (!document || !document->view())
>         return Exception { InvalidAccessError };
> 
>-    element.scrollTo({ x, y }, ScrollClamping::Unclamped);
>+    element.scrollTo(fromCoordinates(x, y), ScrollClamping::Unclamped);
>     return { };
> }
> 
>diff --git a/Source/WebKit/Configurations/FeatureDefines.xcconfig b/Source/WebKit/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..211a58e967f 100644
>--- a/Source/WebKit/Configurations/FeatureDefines.xcconfig
>+++ b/Source/WebKit/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_SMOOTH_SCROLLING = ENABLE_CSSOM_SMOOTH_SCROLLING;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_SMOOTH_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>diff --git a/Source/WebKit/Shared/WebPreferences.yaml b/Source/WebKit/Shared/WebPreferences.yaml
>index 10f49ba4609..49ade9af573 100644
>--- a/Source/WebKit/Shared/WebPreferences.yaml
>+++ b/Source/WebKit/Shared/WebPreferences.yaml
>@@ -1139,6 +1139,13 @@ AsyncFrameScrollingEnabled:
>   humanReadableDescription: "Perform frame scrolling in a dedicated thread or process"
>   category: experimental
> 
>+CSSomSmoothScrollingEnabled:
>+  type: bool
>+  defaultValue: false
>+  humanReadableName: "CSSOM Smooth Scrolling"
>+  humanReadableDescription: "Enabled DOM API and CSS property for 'smooth' scroll behavior"
>+  category: experimental
>+
> SpringTimingFunctionEnabled:
>   type: bool
>   defaultValue: DEFAULT_EXPERIMENTAL_FEATURES_ENABLED
>diff --git a/Source/WebKitLegacy/mac/Configurations/FeatureDefines.xcconfig b/Source/WebKitLegacy/mac/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..211a58e967f 100644
>--- a/Source/WebKitLegacy/mac/Configurations/FeatureDefines.xcconfig
>+++ b/Source/WebKitLegacy/mac/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_SMOOTH_SCROLLING = ENABLE_CSSOM_SMOOTH_SCROLLING;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_SMOOTH_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>diff --git a/Source/cmake/WebKitFeatures.cmake b/Source/cmake/WebKitFeatures.cmake
>index b70b6166ad6..870c344c511 100644
>--- a/Source/cmake/WebKitFeatures.cmake
>+++ b/Source/cmake/WebKitFeatures.cmake
>@@ -162,6 +162,7 @@ macro(WEBKIT_OPTION_BEGIN)
>     WEBKIT_OPTION_DEFINE(ENABLE_SERVICE_CONTROLS "Toggle service controls support" PRIVATE OFF)
>     WEBKIT_OPTION_DEFINE(ENABLE_SERVICE_WORKER "Toggle ServiceWorker support" PRIVATE OFF)
>     WEBKIT_OPTION_DEFINE(ENABLE_SMOOTH_SCROLLING "Toggle smooth scrolling" PRIVATE ON)
>+    WEBKIT_OPTION_DEFINE(ENABLE_CSSOM_SMOOTH_SCROLLING "Toggle CSSOM smooth scrolling support" PRIVATE ON)
>     WEBKIT_OPTION_DEFINE(ENABLE_SPEECH_SYNTHESIS "Toggle Speech Synthesis API support" PRIVATE OFF)
>     WEBKIT_OPTION_DEFINE(ENABLE_SPELLCHECK "Toggle Spellchecking support (requires Enchant)" PRIVATE OFF)
>     WEBKIT_OPTION_DEFINE(ENABLE_STREAMS_API "Toggle Streams API support" PRIVATE ON)
>diff --git a/Source/cmake/tools/vsprops/FeatureDefines.props b/Source/cmake/tools/vsprops/FeatureDefines.props
>index 4d42faa9b55..db9d4d0cd5d 100644
>--- a/Source/cmake/tools/vsprops/FeatureDefines.props
>+++ b/Source/cmake/tools/vsprops/FeatureDefines.props
>@@ -4,6 +4,7 @@
>     <ENABLE_3D_TRANSFORMS>ENABLE_3D_TRANSFORMS</ENABLE_3D_TRANSFORMS>
>     <ENABLE_ACCELERATED_2D_CANVAS />
>     <ENABLE_ACCELERATED_OVERFLOW_SCROLLING />
>+    <ENABLE_CSSOM_SMOOTH_SCROLLING>ENABLE_CSSOM_SMOOTH_SCROLLING</ENABLE_CSSOM_SMOOTH_SCROLLING>
>     <ENABLE_ATTACHMENT_ELEMENT>ENABLE_ATTACHMENT_ELEMENT</ENABLE_ATTACHMENT_ELEMENT>
>     <ENABLE_CHANNEL_MESSAGING>ENABLE_CHANNEL_MESSAGING</ENABLE_CHANNEL_MESSAGING>
>     <ENABLE_CSS3_CONDITIONAL_RULES>ENABLE_CSS3_CONDITIONAL_RULES</ENABLE_CSS3_CONDITIONAL_RULES>
>@@ -76,7 +77,7 @@
>   </PropertyGroup>
>   <ItemDefinitionGroup>
>     <ClCompile>
>-      <PreprocessorDefinitions>$(ENABLE_3D_TRANSFORMS);$(ENABLE_ACCELERATED_2D_CANVAS);$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING);$(ENABLE_ATTACHMENT_ELEMENT);$(ENABLE_CHANNEL_MESSAGING);$(ENABLE_CSS3_CONDITIONAL_RULES);$(ENABLE_CSS_IMAGE_SET);$(ENABLE_CSS3_TEXT);$(ENABLE_CSS_BOX_DECORATION_BREAK);$(ENABLE_CSS_SHADERS);$(ENABLE_CSS_COMPOSITING);$(ENABLE_CSS_SELECTORS_LEVEL4);$(ENABLE_CSS_SHAPE_INSIDE);$(ENABLE_CSS_TRANSFORMS_ANIMATIONS_TRANSITIONS_UNPREFIXED);$(ENABLE_CURSOR_VISIBILITY);$(ENABLE_CUSTOM_SCHEME_HANDLER);$(ENABLE_DATAGRID);$(ENABLE_DATALIST_ELEMENT);$(ENABLE_DEVICE_ORIENTATION);$(ENABLE_DIRECTORY_UPLOAD);$(ENABLE_ENCRYPTED_MEDIA);$(ENABLE_FETCH_API);$(ENABLE_FILE_SYSTEM);$(ENABLE_FULLSCREEN_API);$(ENABLE_GAMEPAD);$(ENABLE_GEOLOCATION);$(ENABLE_HIGH_DPI_CANVAS);$(ENABLE_ICONDATABASE);$(ENABLE_INDEXED_DATABASE);$(ENABLE_INPUT_TYPE_COLOR);$(ENABLE_INPUT_SPEECH);$(ENABLE_INPUT_TYPE_DATE);$(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE);$(ENABLE_INPUT_TYPE_DATETIMELOCAL);$(ENABLE_INPUT_TYPE_MONTH);$(ENABLE_INPUT_TYPE_TIME);$(ENABLE_INPUT_TYPE_WEEK);$(ENABLE_INTL);$(ENABLE_LEGACY_CSS_VENDOR_PREFIXES);$(ENABLE_LEGACY_ENCRYPTED_MEDIA);$(ENABLE_LINK_PRERENDER);$(ENABLE_MATHML);$(ENABLE_METER_ELEMENT);$(ENABLE_MICRODATA);$(ENABLE_MOUSE_CURSOR_SCALE);$(ENABLE_NOTIFICATIONS);$(ENABLE_QUOTA);$(ENABLE_NAVIGATOR_CONTENT_UTILS);$(ENABLE_STREAMS_API);$(ENABLE_SCRIPTED_SPEECH);$(ENABLE_SHARED_WORKERS);$(ENABLE_MEDIA_CONTROLS_SCRIPT);$(ENABLE_MEDIA_SOURCE);$(ENABLE_MEDIA_STATISTICS);$(ENABLE_SQL_DATABASE);$(ENABLE_STYLE_SCOPED);$(ENABLE_SUBPIXEL_LAYOUT);$(ENABLE_SVG_DOM_OBJC_BINDINGS);$(ENABLE_SVG_FONTS);$(ENABLE_VIDEO);$(ENABLE_VIDEO_TRACK);$(ENABLE_WEB_AUDIO);$(ENABLE_WEBGL);$(ENABLE_WEBGPU);$(ENABLE_WEBVTT_REGIONS);$(ENABLE_XHR_TIMEOUT);$(ENABLE_XSLT);%(PreprocessorDefinitions)</PreprocessorDefinitions>
>+      <PreprocessorDefinitions>$(ENABLE_3D_TRANSFORMS);$(ENABLE_ACCELERATED_2D_CANVAS);$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING);$(ENABLE_CSSOM_SMOOTH_SCROLLING);$(ENABLE_ATTACHMENT_ELEMENT);$(ENABLE_CHANNEL_MESSAGING);$(ENABLE_CSS3_CONDITIONAL_RULES);$(ENABLE_CSS_IMAGE_SET);$(ENABLE_CSS3_TEXT);$(ENABLE_CSS_BOX_DECORATION_BREAK);$(ENABLE_CSS_SHADERS);$(ENABLE_CSS_COMPOSITING);$(ENABLE_CSS_SELECTORS_LEVEL4);$(ENABLE_CSS_SHAPE_INSIDE);$(ENABLE_CSS_TRANSFORMS_ANIMATIONS_TRANSITIONS_UNPREFIXED);$(ENABLE_CURSOR_VISIBILITY);$(ENABLE_CUSTOM_SCHEME_HANDLER);$(ENABLE_DATAGRID);$(ENABLE_DATALIST_ELEMENT);$(ENABLE_DEVICE_ORIENTATION);$(ENABLE_DIRECTORY_UPLOAD);$(ENABLE_ENCRYPTED_MEDIA);$(ENABLE_FETCH_API);$(ENABLE_FILE_SYSTEM);$(ENABLE_FULLSCREEN_API);$(ENABLE_GAMEPAD);$(ENABLE_GEOLOCATION);$(ENABLE_HIGH_DPI_CANVAS);$(ENABLE_ICONDATABASE);$(ENABLE_INDEXED_DATABASE);$(ENABLE_INPUT_TYPE_COLOR);$(ENABLE_INPUT_SPEECH);$(ENABLE_INPUT_TYPE_DATE);$(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE);$(ENABLE_INPUT_TYPE_DATETIMELOCAL);$(ENABLE_INPUT_TYPE_MONTH);$(ENABLE_INPUT_TYPE_TIME);$(ENABLE_INPUT_TYPE_WEEK);$(ENABLE_INTL);$(ENABLE_LEGACY_CSS_VENDOR_PREFIXES);$(ENABLE_LEGACY_ENCRYPTED_MEDIA);$(ENABLE_LINK_PRERENDER);$(ENABLE_MATHML);$(ENABLE_METER_ELEMENT);$(ENABLE_MICRODATA);$(ENABLE_MOUSE_CURSOR_SCALE);$(ENABLE_NOTIFICATIONS);$(ENABLE_QUOTA);$(ENABLE_NAVIGATOR_CONTENT_UTILS);$(ENABLE_STREAMS_API);$(ENABLE_SCRIPTED_SPEECH);$(ENABLE_SHARED_WORKERS);$(ENABLE_MEDIA_CONTROLS_SCRIPT);$(ENABLE_MEDIA_SOURCE);$(ENABLE_MEDIA_STATISTICS);$(ENABLE_SQL_DATABASE);$(ENABLE_STYLE_SCOPED);$(ENABLE_SUBPIXEL_LAYOUT);$(ENABLE_SVG_DOM_OBJC_BINDINGS);$(ENABLE_SVG_FONTS);$(ENABLE_VIDEO);$(ENABLE_VIDEO_TRACK);$(ENABLE_WEB_AUDIO);$(ENABLE_WEBGL);$(ENABLE_WEBGPU);$(ENABLE_WEBVTT_REGIONS);$(ENABLE_XHR_TIMEOUT);$(ENABLE_XSLT);%(PreprocessorDefinitions)</PreprocessorDefinitions>
>     </ClCompile>
>   </ItemDefinitionGroup>
>   <ItemGroup>
>@@ -92,6 +93,10 @@
>       <Value>$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING)</Value>
>       <EnvironmentVariable>true</EnvironmentVariable>
>     </BuildMacro>
>+    <BuildMacro Include="ENABLE_CSSOM_SMOOTH_SCROLLING">
>+      <Value>$(ENABLE_CSSOM_SMOOTH_SCROLLING)</Value>
>+      <EnvironmentVariable>true</EnvironmentVariable>
>+    </BuildMacro>
>     <BuildMacro Include="ENABLE_ATTACHMENT_ELEMENT">
>       <Value>$(ENABLE_ATTACHMENT_ELEMENT)</Value>
>       <EnvironmentVariable>true</EnvironmentVariable>
>diff --git a/Source/cmake/tools/vsprops/FeatureDefinesCairo.props b/Source/cmake/tools/vsprops/FeatureDefinesCairo.props
>index 113aade5c8f..75ee1b2a621 100644
>--- a/Source/cmake/tools/vsprops/FeatureDefinesCairo.props
>+++ b/Source/cmake/tools/vsprops/FeatureDefinesCairo.props
>@@ -4,6 +4,7 @@
>     <ENABLE_3D_TRANSFORMS>ENABLE_3D_TRANSFORMS</ENABLE_3D_TRANSFORMS>
>     <ENABLE_ACCELERATED_2D_CANVAS />
>     <ENABLE_ACCELERATED_OVERFLOW_SCROLLING />
>+    <ENABLE_CSSOM_SMOOTH_SCROLLING>ENABLE_CSSOM_SMOOTH_SCROLLING</ENABLE_CSSOM_SMOOTH_SCROLLING>
>     <ENABLE_ATTACHMENT_ELEMENT>ENABLE_ATTACHMENT_ELEMENT</ENABLE_ATTACHMENT_ELEMENT>
>     <ENABLE_CHANNEL_MESSAGING>ENABLE_CHANNEL_MESSAGING</ENABLE_CHANNEL_MESSAGING>
>     <ENABLE_CSS3_CONDITIONAL_RULES>ENABLE_CSS3_CONDITIONAL_RULES</ENABLE_CSS3_CONDITIONAL_RULES>
>@@ -75,7 +76,7 @@
>   </PropertyGroup>
>   <ItemDefinitionGroup>
>     <ClCompile>
>-      <PreprocessorDefinitions>$(ENABLE_3D_TRANSFORMS);$(ENABLE_ACCELERATED_2D_CANVAS);$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING);$(ENABLE_ATTACHMENT_ELEMENT);$(ENABLE_CHANNEL_MESSAGING);$(ENABLE_CSS3_CONDITIONAL_RULES);$(ENABLE_CSS_IMAGE_SET);$(ENABLE_CSS3_TEXT);$(ENABLE_CSS_BOX_DECORATION_BREAK);$(ENABLE_CSS_SHADERS);$(ENABLE_CSS_COMPOSITING);$(ENABLE_CSS_SELECTORS_LEVEL4);$(ENABLE_CSS_SHAPE_INSIDE);$(ENABLE_CSS_TRANSFORMS_ANIMATIONS_TRANSITIONS_UNPREFIXED);$(ENABLE_CURSOR_VISIBILITY);$(ENABLE_CUSTOM_SCHEME_HANDLER);$(ENABLE_DATAGRID);$(ENABLE_DATALIST_ELEMENT);$(ENABLE_DEVICE_ORIENTATION);$(ENABLE_DIRECTORY_UPLOAD);$(ENABLE_ENCRYPTED_MEDIA);$(ENABLE_FETCH_API);$(ENABLE_FILE_SYSTEM);$(ENABLE_FULLSCREEN_API);$(ENABLE_GAMEPAD);$(ENABLE_GEOLOCATION);$(ENABLE_HIGH_DPI_CANVAS);$(ENABLE_ICONDATABASE);$(ENABLE_INDEXED_DATABASE);$(ENABLE_INPUT_TYPE_COLOR);$(ENABLE_INPUT_SPEECH);$(ENABLE_INPUT_TYPE_DATE);$(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE);$(ENABLE_INPUT_TYPE_DATETIMELOCAL);$(ENABLE_INPUT_TYPE_MONTH);$(ENABLE_INPUT_TYPE_TIME);$(ENABLE_INPUT_TYPE_WEEK);$(ENABLE_INTL);$(ENABLE_LEGACY_CSS_VENDOR_PREFIXES);$(ENABLE_LEGACY_ENCRYPTED_MEDIA);$(ENABLE_LINK_PRERENDER);$(ENABLE_MATHML);$(ENABLE_METER_ELEMENT);$(ENABLE_MICRODATA);$(ENABLE_MOUSE_CURSOR_SCALE);$(ENABLE_NOTIFICATIONS);$(ENABLE_QUOTA);$(ENABLE_NAVIGATOR_CONTENT_UTILS);$(ENABLE_SCRIPTED_SPEECH);$(ENABLE_SHARED_WORKERS);$(ENABLE_MEDIA_CONTROLS_SCRIPT);$(ENABLE_MEDIA_SOURCE);$(ENABLE_MEDIA_STATISTICS);$(ENABLE_SQL_DATABASE);$(ENABLE_STYLE_SCOPED);$(ENABLE_SUBPIXEL_LAYOUT);$(ENABLE_SVG_DOM_OBJC_BINDINGS);$(ENABLE_SVG_FONTS);$(ENABLE_VIDEO);$(ENABLE_VIDEO_TRACK);$(ENABLE_WEB_AUDIO);$(ENABLE_WEBGL);$(ENABLE_WEBVTT_REGIONS);$(ENABLE_XHR_TIMEOUT);$(ENABLE_XSLT);%(PreprocessorDefinitions)</PreprocessorDefinitions>
>+      <PreprocessorDefinitions>$(ENABLE_3D_TRANSFORMS);$(ENABLE_ACCELERATED_2D_CANVAS);$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING);$(ENABLE_CSSOM_SMOOTH_SCROLLING);$(ENABLE_ATTACHMENT_ELEMENT);$(ENABLE_CHANNEL_MESSAGING);$(ENABLE_CSS3_CONDITIONAL_RULES);$(ENABLE_CSS_IMAGE_SET);$(ENABLE_CSS3_TEXT);$(ENABLE_CSS_BOX_DECORATION_BREAK);$(ENABLE_CSS_SHADERS);$(ENABLE_CSS_COMPOSITING);$(ENABLE_CSS_SELECTORS_LEVEL4);$(ENABLE_CSS_SHAPE_INSIDE);$(ENABLE_CSS_TRANSFORMS_ANIMATIONS_TRANSITIONS_UNPREFIXED);$(ENABLE_CURSOR_VISIBILITY);$(ENABLE_CUSTOM_SCHEME_HANDLER);$(ENABLE_DATAGRID);$(ENABLE_DATALIST_ELEMENT);$(ENABLE_DEVICE_ORIENTATION);$(ENABLE_DIRECTORY_UPLOAD);$(ENABLE_ENCRYPTED_MEDIA);$(ENABLE_FETCH_API);$(ENABLE_FILE_SYSTEM);$(ENABLE_FULLSCREEN_API);$(ENABLE_GAMEPAD);$(ENABLE_GEOLOCATION);$(ENABLE_HIGH_DPI_CANVAS);$(ENABLE_ICONDATABASE);$(ENABLE_INDEXED_DATABASE);$(ENABLE_INPUT_TYPE_COLOR);$(ENABLE_INPUT_SPEECH);$(ENABLE_INPUT_TYPE_DATE);$(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE);$(ENABLE_INPUT_TYPE_DATETIMELOCAL);$(ENABLE_INPUT_TYPE_MONTH);$(ENABLE_INPUT_TYPE_TIME);$(ENABLE_INPUT_TYPE_WEEK);$(ENABLE_INTL);$(ENABLE_LEGACY_CSS_VENDOR_PREFIXES);$(ENABLE_LEGACY_ENCRYPTED_MEDIA);$(ENABLE_LINK_PRERENDER);$(ENABLE_MATHML);$(ENABLE_METER_ELEMENT);$(ENABLE_MICRODATA);$(ENABLE_MOUSE_CURSOR_SCALE);$(ENABLE_NOTIFICATIONS);$(ENABLE_QUOTA);$(ENABLE_NAVIGATOR_CONTENT_UTILS);$(ENABLE_SCRIPTED_SPEECH);$(ENABLE_SHARED_WORKERS);$(ENABLE_MEDIA_CONTROLS_SCRIPT);$(ENABLE_MEDIA_SOURCE);$(ENABLE_MEDIA_STATISTICS);$(ENABLE_SQL_DATABASE);$(ENABLE_STYLE_SCOPED);$(ENABLE_SUBPIXEL_LAYOUT);$(ENABLE_SVG_DOM_OBJC_BINDINGS);$(ENABLE_SVG_FONTS);$(ENABLE_VIDEO);$(ENABLE_VIDEO_TRACK);$(ENABLE_WEB_AUDIO);$(ENABLE_WEBGL);$(ENABLE_WEBVTT_REGIONS);$(ENABLE_XHR_TIMEOUT);$(ENABLE_XSLT);%(PreprocessorDefinitions)</PreprocessorDefinitions>
>     </ClCompile>
>   </ItemDefinitionGroup>
>   <ItemGroup>
>@@ -91,6 +92,10 @@
>       <Value>$(ENABLE_ACCELERATED_OVERFLOW_SCROLLING)</Value>
>       <EnvironmentVariable>true</EnvironmentVariable>
>     </BuildMacro>
>+    <BuildMacro Include="ENABLE_CSSOM_SMOOTH_SCROLLING">
>+      <Value>$(ENABLE_CSSOM_SMOOTH_SCROLLING)</Value>
>+      <EnvironmentVariable>true</EnvironmentVariable>
>+    </BuildMacro>
>     <BuildMacro Include="ENABLE_ATTACHMENT_ELEMENT">
>       <Value>$(ENABLE_ATTACHMENT_ELEMENT)</Value>
>       <EnvironmentVariable>true</EnvironmentVariable>
>diff --git a/Tools/Scripts/webkitperl/FeatureList.pm b/Tools/Scripts/webkitperl/FeatureList.pm
>index 6c9060d020d..4f09413a7e7 100644
>--- a/Tools/Scripts/webkitperl/FeatureList.pm
>+++ b/Tools/Scripts/webkitperl/FeatureList.pm
>@@ -118,6 +118,7 @@ my (
>     $resolutionMediaQuerySupport,
>     $scriptedSpeechSupport,
>     $serviceWorkerSupport,
>+    $cssomSmoothScrollingSupport,
>     $subtleCrypto,
>     $svgFontsSupport,
>     $systemMallocSupport,
>@@ -337,6 +338,9 @@ my @features = (
>     { option => "service-worker", desc => "Toggle Service Worker support",
>       define => "ENABLE_SERVICE_WORKER", value => \$serviceWorkerSupport },
> 
>+    { option => "cssom-smooth-scrolling", desc => "Toggle CSSOM Smooth Scroling support",
>+      define => "ENABLE_CSSOM_SMOOTH_SCROLLING", value => \$cssomSmoothScrollingSupport },
>+
>     { option => "subtle-crypto", desc => "Toggle WebCrypto Subtle-Crypto support",
>       define => "ENABLE_SUBTLE_CRYPTO", value => \$subtleCrypto },
> 
>diff --git a/Tools/TestWebKitAPI/Configurations/FeatureDefines.xcconfig b/Tools/TestWebKitAPI/Configurations/FeatureDefines.xcconfig
>index dfa4a259773..211a58e967f 100644
>--- a/Tools/TestWebKitAPI/Configurations/FeatureDefines.xcconfig
>+++ b/Tools/TestWebKitAPI/Configurations/FeatureDefines.xcconfig
>@@ -40,6 +40,8 @@ ENABLE_ACCELERATED_2D_CANVAS = ;
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING = $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING_$(WK_COCOA_TOUCH));
> ENABLE_ACCELERATED_OVERFLOW_SCROLLING_cocoatouch = ENABLE_ACCELERATED_OVERFLOW_SCROLLING;
> 
>+ENABLE_CSSOM_SMOOTH_SCROLLING = ENABLE_CSSOM_SMOOTH_SCROLLING;
>+
> ENABLE_APPLE_PAY = $(ENABLE_APPLE_PAY_$(WK_PLATFORM_NAME));
> ENABLE_APPLE_PAY_iphoneos = ENABLE_APPLE_PAY;
> ENABLE_APPLE_PAY_iphonesimulator = ENABLE_APPLE_PAY;
>@@ -374,4 +376,4 @@ ENABLE_WIRELESS_PLAYBACK_TARGET = ENABLE_WIRELESS_PLAYBACK_TARGET;
> 
> ENABLE_XSLT = ENABLE_XSLT;
> 
>-FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);
>+FEATURE_DEFINES = $(ENABLE_3D_TRANSFORMS) $(ENABLE_ACCELERATED_2D_CANVAS) $(ENABLE_ACCELERATED_OVERFLOW_SCROLLING) $(ENABLE_CSSOM_SMOOTH_SCROLLING) $(ENABLE_APPLE_PAY) $(ENABLE_APPLE_PAY_SESSION_V3) $(ENABLE_APPLE_PAY_SESSION_V4) $(ENABLE_APPLICATION_MANIFEST) $(ENABLE_ATTACHMENT_ELEMENT) $(ENABLE_AVF_CAPTIONS) $(ENABLE_CACHE_PARTITIONING) $(ENABLE_CHANNEL_MESSAGING) $(ENABLE_CONTENT_FILTERING) $(ENABLE_CSS3_TEXT) $(ENABLE_CSS_ANIMATIONS_LEVEL_2) $(ENABLE_CSS_BOX_DECORATION_BREAK) $(ENABLE_CSS_COMPOSITING) $(ENABLE_CSS_DEVICE_ADAPTATION) $(ENABLE_CSS_IMAGE_ORIENTATION) $(ENABLE_CSS_IMAGE_RESOLUTION) $(ENABLE_CSS_SCROLL_SNAP) $(ENABLE_CSS_SELECTORS_LEVEL4) $(ENABLE_CSS_TRAILING_WORD) $(ENABLE_CURSOR_VISIBILITY) $(ENABLE_CUSTOM_SCHEME_HANDLER) $(ENABLE_DASHBOARD_SUPPORT) $(ENABLE_DATA_INTERACTION) $(ENABLE_DATACUE_VALUE) $(ENABLE_DATALIST_ELEMENT) $(ENABLE_DEVICE_ORIENTATION) $(ENABLE_DRAG_SUPPORT) $(ENABLE_ENCRYPTED_MEDIA) $(ENABLE_EXPERIMENTAL_FEATURES) $(ENABLE_FAST_JIT_PERMISSIONS) $(ENABLE_FILTERS_LEVEL_2) $(ENABLE_FTL_JIT) $(ENABLE_FULLSCREEN_API) $(ENABLE_GAMEPAD) $(ENABLE_GEOLOCATION) $(ENABLE_ICONDATABASE) $(ENABLE_INDEXED_DATABASE) $(ENABLE_INDEXED_DATABASE_IN_WORKERS) $(ENABLE_INPUT_TYPE_COLOR) $(ENABLE_INPUT_TYPE_DATE) $(ENABLE_INPUT_TYPE_DATETIME_INCOMPLETE) $(ENABLE_INPUT_TYPE_DATETIMELOCAL) $(ENABLE_INPUT_TYPE_MONTH) $(ENABLE_INPUT_TYPE_TIME) $(ENABLE_INPUT_TYPE_WEEK) $(ENABLE_INTERSECTION_OBSERVER) $(ENABLE_INTL) $(ENABLE_IOS_GESTURE_EVENTS) $(ENABLE_IOS_TOUCH_EVENTS) $(ENABLE_JIT) $(ENABLE_JS_ASYNC_ITERATION) $(ENABLE_KEYBOARD_CODE_ATTRIBUTE) $(ENABLE_KEYBOARD_KEY_ATTRIBUTE) $(ENABLE_LAYOUT_FORMATTING_CONTEXT) $(ENABLE_LEGACY_CSS_VENDOR_PREFIXES) $(ENABLE_LEGACY_CUSTOM_PROTOCOL_MANAGER) $(ENABLE_LEGACY_ENCRYPTED_MEDIA) $(ENABLE_LETTERPRESS) $(ENABLE_MAC_GESTURE_EVENTS) $(ENABLE_MAC_VIDEO_TOOLBOX) $(ENABLE_MATHML) $(ENABLE_MEDIA_CAPTURE) $(ENABLE_MEDIA_CONTROLS_SCRIPT) $(ENABLE_MEDIA_SESSION) $(ENABLE_MEDIA_SOURCE) $(ENABLE_MEDIA_STATISTICS) $(ENABLE_MEDIA_STREAM) $(ENABLE_METER_ELEMENT) $(ENABLE_MHTML) $(ENABLE_MOUSE_CURSOR_SCALE) $(ENABLE_NAVIGATOR_CONTENT_UTILS) $(ENABLE_NAVIGATOR_STANDALONE) $(ENABLE_NOTIFICATIONS) $(ENABLE_PAYMENT_REQUEST) $(ENABLE_PDFKIT_PLUGIN) $(ENABLE_POINTER_LOCK) $(ENABLE_PUBLIC_SUFFIX_LIST) $(ENABLE_QUOTA) $(ENABLE_REMOTE_INSPECTOR) $(ENABLE_RESOLUTION_MEDIA_QUERY) $(ENABLE_RESOURCE_USAGE) $(ENABLE_RUBBER_BANDING) $(ENABLE_SERVICE_CONTROLS) $(ENABLE_SERVICE_WORKER) $(ENABLE_SPEECH_SYNTHESIS) $(ENABLE_STREAMS_API) $(ENABLE_SUBTLE_CRYPTO) $(ENABLE_SVG_FONTS) $(ENABLE_TELEPHONE_NUMBER_DETECTION) $(ENABLE_TEXT_AUTOSIZING) $(ENABLE_TOUCH_EVENTS) $(ENABLE_USER_MESSAGE_HANDLERS) $(ENABLE_USERSELECT_ALL) $(ENABLE_VARIATION_FONTS) $(ENABLE_VIDEO) $(ENABLE_VIDEO_PRESENTATION_MODE) $(ENABLE_VIDEO_TRACK) $(ENABLE_VIDEO_USES_ELEMENT_FULLSCREEN) $(ENABLE_WEB_AUDIO) $(ENABLE_WEB_AUTHN) $(ENABLE_WEB_RTC) $(ENABLE_WEBASSEMBLY) $(ENABLE_WEBASSEMBLY_STREAMING_API) $(ENABLE_WEBGL) $(ENABLE_WEBGL2) $(ENABLE_WEBGPU) $(ENABLE_WIRELESS_PLAYBACK_TARGET) $(ENABLE_XSLT);

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