Add about://flags entry for tab groups.

Bug: 905491
Change-Id: Ia683bc7465b3d5987ec80f2f01b13b99b5374746
Reviewed-on: https://chromium-review.googlesource.com/c/1343363
Commit-Queue: Taylor Bergquist <tbergquist@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Bret Sepulveda <bsep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#613784}
7 files changed