Add pixel readback to page popup

BUG=409503

Review URL: https://codereview.chromium.org/513723003

git-svn-id: svn://svn.chromium.org/blink/trunk@182027 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Use AcceleratedImageBufferSurfaces for video texImage2D calls.

This un-deletes AcceleratedImageBufferSurface and uses it when copying
video frames to WebGL via TexImage2d.

This allows the WebMediaPlayer to do YUV conversion on the GPU,
resulting in significant speedups.

https://codereview.chromium.org/531353002/ on the Chromium side is
necessary for this performance improvement to take effect.

On the Skia side, https://codereview.chromium.org/516463005/ will need
to land in order for this to affect videos of the most common YUV
color space.

BUG=91208

Review URL: https://codereview.chromium.org/565743003

git-svn-id: svn://svn.chromium.org/blink/trunk@182029 bbb929c8-8fbe-4397-9dbb-9b2b20218538