GitLab

This change:
* removes COLOR_TAB_TEXT_INACTIVE and instead simply alpha-blends
  COLOR_TAB_TEXT
* removes disabled unit test that uses COLOR_TAB_TEXT_INACTIVE
* uses COLOR_BACKGROUND_TAB_TEXT_INACTIVE directly if a theme
  provides it

Bug: 901610, 859243
Change-Id: I7db13a7719284ac3e27ec3bfc122d6381430df26
Reviewed-on: https://chromium-review.googlesource.com/c/1334419
Commit-Queue: Collin Baker <collinbaker@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608831}