GitLab

This CL:
  - Removes support for non-GRID tab switchers from the feature engagement egtest.
  - Simplifies tab_usage_recorder_test_util to only support the tab grid.
  - Removes non-grid support from the UKM egtest
  - Moves the TabletTabSwitcherOpenButton() helper function to chrome_matchers, out of the moribund tab_switcher/ directory.


Cq-Include-Trybots: luci.chromium.try:ios-simulator-cronet;luci.chromium.try:ios-simulator-full-configs
Change-Id: I6cbcfa88f13bdad6407e56746e9e76bd9e4a5d38
Reviewed-on: https://chromium-review.googlesource.com/1233195
Commit-Queue: Mark Cogan <marq@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592824}