Remove imports of `dart:io` from `test.dart` unless its available (da…

…rt-lang#933)

update sdk constraint to <3.0.0 (dart-lang#905)

Add support for loading precompiled kernel files for vm tests (dart-l…

…ang#896)

* support loading .vm.app.dill files in precompiled mode

* add a test for loading from dill files

* update pubspec/changelog for 1.2.0 release

prep-for-1.0.0 (dart-lang#886)

prep for release (dart-lang#883)

prep for release (dart-lang#879)

Report original test location in the json_reporter if different (dart…

…-lang#853)

* add root_line, root_column, and root_package_url to the json reporter

* update docs, pubspec, changelog

More Dart 2 runtime semantic fixes (dart-lang#844)

```
type 'WebSocketChannel' is not a subtype of type 'StreamChannel<String>' of 'channel'
```

Cast the `WebSocketChannel` to indicate that all values in each
direction will be `String`.

```
type 'CloseGuaranteeChannel<dynamic>' is not a subtype of type 'VirtualChannel'
```

Avoid using the `suiteChannel` variable for two types. It needs to start
as a `VirtualChannel` which has the `id` field, and then later be a
`StreamChannel`.

```
type 'RunnerSuite' is not a subtype of type 'FutureOr<Future<RunnerSuite>>'
```

Avoid the attempted Future flattening which was never correct but was
supported in the Dart 1 VM.