We need to make sure we understand the "copyToTexture" (aka copyFromTextureSource aka copyImageBitmapToTexture) interactions with high-bit-depth source data (particularly coming from images, but also canvases).

Today, copyToTexture does allow copying to high-bit-depth formats.
We should make sure we don't ship with paths that take HBD images, convert to LBD data, then upload to HBD formats lossily. Doing so would make it a breaking change to implement the correct behavior later. We may need some feature detection (or at least validation) around this if we don't want to require it off the bat.

cc @shrekshao who is working on EXT_texture_norm16/_dom_source in WebGL.