Port XRWebGLDrawingBuffer to shared images.

Instead of allocating a GL texture that we then Produce, we allocate the
ColorBuffers as shared images that we then import into a GL texture,
taking a Read/Write access scope while the ColorBuffer is used as a back
buffer.

Bug: 962678
Change-Id: Ibe64b8be34144040701ec8ddfbdfdc3a855d55e9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1620942
Auto-Submit: Antoine Labour <piman@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Bill Orr <billorr@chromium.org>
Reviewed-by: Brandon Jones <bajones@chromium.org>
Commit-Queue: Brandon Jones <bajones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#661841}
2 files changed