[Mac] Use SRGB color space when converting from SkColor to CGColor

This fixes flashes when opening themed or incognito NTPs:
TabContentsController::updateBackgroundColorFromWindowTheme uses
skia::CGColorCreateFromSkColor to convert the background color from
SkColor to CGColor, which used the "Generic RGB" color space before.
This does not match SRGB, which is what the NTP (or any WebContents)
uses, as far as I can tell.
This CL fixes the discrepancy by making CGColorCreateFromSkColor use
SRGB.

Bug: 21798, 254361, 719236
Change-Id: I14b03690f585d266b6329d6b19b37ee8ac36c6ce
Reviewed-on: https://chromium-review.googlesource.com/842646
Reviewed-by: Justin Novosad <junov@chromium.org>
Reviewed-by: ccameron <ccameron@chromium.org>
Commit-Queue: Marc Treib <treib@chromium.org>
Cr-Commit-Position: refs/heads/master@{#529390}
2 files changed