GitLab

This allows the zero-copy construction of RGB frames from CPU backed
ImageBitmaps and removes a copy from YUV backed ImageBitmaps. As the
formats are now supported, planar access is enabled.

Encoding support is enabled by teaching the utility method used by
the encoders how to scale and convert RGB frames to I420 and NV12.

Fixed: 1161012
Test: https://storage.googleapis.com/dalecurtis/canvas-test.html
Change-Id: I3944a4903b8defc5592ba65d4536ec4d0750c861
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2601678
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Eugene Zemtsov <eugene@chromium.org>
Auto-Submit: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840760}