GitLab

Pushed color calculation logic in GetTabBackgroundColor() down into
ThemeHelper.

Bug: 1056916
Change-Id: I6c6b5a204554b825887b1c306b766e4403609279
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2092199
Commit-Queue: Thomas Lukaszewicz <tluk@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#748889}