Plumb color space into layer tree readback pixel tests.

A soon-upcoming change will complete the color space plumbing in the
viz::DirectRenderers' CopyOutputRequest execution pipelines. Tests will
require that the pixel test infrastructure pass a texture's color space
data through to its SkBitmap readback results.

Bug: 758057
Change-Id: Ica583cbc969e8da9316d1da65a12837f490657fb
Reviewed-on: https://chromium-review.googlesource.com/c/1368411
Reviewed-by: ccameron <ccameron@chromium.org>
Commit-Queue: Yuri Wiitala <miu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614953}
3 files changed