Use EventRewriter to disable system mouse events in Aura SPPHTBTs.

It seems that spurious mousemove events on Win have been creeping into
tests in this suite (e.g. a test window pops up under where the system
thinks the mouse cursor is, and generates a mouse-enter). These events
appear to be at the root of flakes for at least one, and possibly more,
tests in this hierarchy.

This CL installs a ui::EventRewriter that discards all system mouse
events in an attempt to reduce flake in the tests.

Bug: 833380
Change-Id: I48adacad0fdf4126ea4198bfa72b336d0eb63389
Reviewed-on: https://chromium-review.googlesource.com/1194253
Commit-Queue: James MacLean <wjmaclean@chromium.org>
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#587189}
1 file changed