GitLab

This CL adds an experiment flag for Tab Grid,
and simply uses the flag to show a blank tab
grid when enabled.

Bug: 804496
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I9d24d64c77cba8889f2c699763d610617263b9cc
Reviewed-on: https://chromium-review.googlesource.com/917427
Commit-Queue: edchin <edchin@chromium.org>
Reviewed-by: Mark Cogan <marq@chromium.org>
Reviewed-by: edchin <edchin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536751}