commit 0d7ebfdf51a4c76d023b5171172f7a4d6966d3e5
author Peter Kasting <pkasting@chromium.org> Wed Jan 16 16:17:39 2019
committer Commit Bot <commit-bot@chromium.org> Wed Jan 16 16:17:39 2019
tree d64372b2d55ca671299c319e3b06755c7912b96c
parent 200d78d850f5f04322c02bd399e204c3b98b8c2d

Remove GetThemedAssetColor().

This method was first added in http://crrev.com/550045 to fix bug 814121 by
matching Clank behavior.  It was then generalized in http://crrev.com/592661 to
apply to more cases.

Unfortunately, the Clank behavior does not guarantee sufficient contrast to meet
WCAG AA standards.  It guarantees contrast 3 against darker colors, when the
minimum for text is 4.5; and it uses 64% black otherwise, which with the 3
threshold only guarantees a contrast ratio of ~4.

This patch removes the special "themed" path and uses the normal path for
caption colors, and restores auto color readability to labels.  The net result
of this is that:
* On opaque frame (Linux, Win 7 non-Aero, some themes), title and caption
  buttons will use the color that contrasts most with the background, between
  white and GG900 (the Material Refresh "darkest color").
* On glass frame (Win 7 Aero, Win 10), the behavior is very similar, but uses
  black instead of GG900 and a "luma midpoint" instead of luminance midpoint
  check.  These better match native.
* On Ash, caption buttons use GG200 or GG700, but will push the contrast up
  until it reaches at least 3.  Window titles, which use auto color readability,
  will further push the contrast of this color to try and reach 4.5.

Effectively, bug 883177, which was originally fixed by moving Linux and Win 7
toward CrOS, is largely WontFixed, but hopefully the caption button colors and
title text are now more consistent; and bug 814121, which was fixed by matching
Clank, is instead fixed by enforcing minimum contrast ratios.

As a nice bonus, this is noticeably simpler.

Bug: 883177
Change-Id: I0803617c9dfd7e2a27ef399c89ba64d1eec98867
Reviewed-on: https://chromium-review.googlesource.com/c/1407264
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Alan Cutter <alancutter@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623253}