Merges to M46 for:

Merge to M46 for BUG=510252
Add CHROMIUM_ycbcr_422_image extension.

Add an extension that provides a method for GL to process images that
are defined in '2vuy' video format.

GL_YCRCR_422_CHROMIUM <internalformat> as been added and it is an accepted
value when creating an image if the extension is supported.

This extension maps to GL_APPLE_ycbcr_422 and will allow us to determine if
we can use IOSurfaces with that format.

BUG=524582
Review URL: https://codereview.chromium.org/1305153005

Cr-Commit-Position: refs/heads/master@{#345693}
(cherry picked from commit a93c58151c01a8ccc6d98697f04c851f8992ef92)

Committed: https://chromium.googlesource.com/chromium/src/+/320e32bc4fb19ec15c09c2751fe9966a04e08020

[ccameron, 2015-09-09 19:21:44]

Committed patchset #1 (id:1) manually as
320e32bc4fb19ec15c09c2751fe9966a04e08020.