GitLab

This reverts commit d4a087be.

Reason for revert: broken between window drag

Original change's description:
> [Tab Groups] Add animation for tab group headers.
> 
> Bug: 1021689
> 
> Change-Id: Ida4f922471b9e53684acfc683623150b82e2a7cf
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1906873
> Commit-Queue: Charlene Yan <cyan@chromium.org>
> Reviewed-by: Connie Wan <connily@chromium.org>
> Reviewed-by: Taylor Bergquist <tbergquist@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#721269}

TBR=tbergquist@chromium.org,cyan@chromium.org,connily@chromium.org

Change-Id: Iaa871c53373c42e5f55092c97d90e179b6f3862f
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1021689
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1952094Reviewed-by: Charlene Yan <cyan@chromium.org>
Commit-Queue: Charlene Yan <cyan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#721759}