GitLab

These are no longer necessary since PlatformEvent is now a typedef to
ui::Event*.

BUG=none
TEST=compile

Change-Id: I49749511c7db8d0f2f96add58201ad6d288445f3
Reviewed-on: https://chromium-review.googlesource.com/978468
Commit-Queue: Michael Spang <spang@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545807}