A full integration close test is more useful than a showcase test, so I'm updating the title. 

FYI, the first part of updating Showcase was already completed while designing the GridViewControllerDelegate. 

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a749c1d805039e6d0734f6757f7bc824dbd6f032

commit a749c1d805039e6d0734f6757f7bc824dbd6f032
Author: edchin <edchin@chromium.org>
Date: Thu Mar 08 23:19:57 2018

[ios] Add close cell egtest in tab grid

Bug:  804560 
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I8a7f1779aff808edddc525110c8900cbd9fd8b8a
Reviewed-on: https://chromium-review.googlesource.com/955345
Reviewed-by: edchin <edchin@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Commit-Queue: edchin <edchin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541925}
[modify] https://crrev.com/a749c1d805039e6d0734f6757f7bc824dbd6f032/ios/chrome/browser/ui/tab_grid/grid_cell.h
[modify] https://crrev.com/a749c1d805039e6d0734f6757f7bc824dbd6f032/ios/chrome/browser/ui/tab_grid/grid_cell.mm
[modify] https://crrev.com/a749c1d805039e6d0734f6757f7bc824dbd6f032/ios/chrome/browser/ui/tab_grid/grid_constants.h
[modify] https://crrev.com/a749c1d805039e6d0734f6757f7bc824dbd6f032/ios/chrome/browser/ui/tab_grid/grid_constants.mm
[modify] https://crrev.com/a749c1d805039e6d0734f6757f7bc824dbd6f032/ios/chrome/browser/ui/tab_grid/tab_grid_egtest.mm

The NextAction date has arrived: 2018-03-14