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* Fix EventGenerator so that GestureTapDownAndUp and Scroll methods works
on external display.
* Changed the test harness to use the EventGenerator which is
much closer to how home button works.
* Updated AppListTest to use MoveMouseTo and the global event generator.

Bug: 1042754
Change-Id: I33e9696960cd990512847a54a7e487098d73d9dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2008130Reviewed-by: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Alex Newcomer <newcomer@chromium.org>
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738601}