[omnibox] Add flag to toggle tab switch reverse logic

Adds an official flag to toggle experimental behavior of reversing the
tab switch button logic.

Bug: 920628
Change-Id: Id1ba03b912d38225b359d16913b90a61ca0b609c
Reviewed-on: https://chromium-review.googlesource.com/c/1467444
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: manuk hovanesian <manukh@chromium.org>
Commit-Queue: Kevin Bailey <krb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631500}
5 files changed