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This is the final phase of tab-dragging with touch on Mash.
This makes several changes to use the result of the previous
phases and achieve tab-dragging with touch on Mash.

BUG=867074
TEST=manually

Change-Id: I53239efbdf567754d3e9322b334d0a4e6751fa52
Reviewed-on: https://chromium-review.googlesource.com/c/1247034
Commit-Queue: Jun Mukai <mukai@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#599820}