Add a feature flag TabToGTSAnimation

This feature controls whether to show the tab-to-GTS transition
animation.

Bug: 964406
Change-Id: Ibcaa215f9c3025f5d0fb69c9c3ad1431ccb4b85c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1622923
Commit-Queue: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#662310}
8 files changed