GitLab

See https://docs.google.com/document/d/1DFKZsXCU4GySB9Ry8Bhd8k8sB7pO5wOz0GBcFmAq5B4/edit#heading=h.ekjb61oacmwf
for the colors of kProminentIconButton.

Bug: 982950
Change-Id: I921c053c2fcd5c6a30dcf26acc995ce060a90e67
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1775499Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Commit-Queue: Min Chen <minch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#692164}