GitLab

- Live update the colors of splitview divider and splitview divider
  handler bar.
- Remove RoundedRectView. Replace it with CreateRoundedRectBackground.

Bug: 1131543
Change-Id: If0adeaa835aafb28b6d31ffb7a93f816a8900012
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2531188Reviewed-by: Xiaoqian Dai <xdai@chromium.org>
Commit-Queue: Min Chen <minch@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826470}