Remove ShelfBezelEventHandler

This is no longer necessary.

Bug: 984347
Test: updated the test. no functional change.

Change-Id: Ia1ae37b6ed9a84af49ce5e6ab3025f0d9cb13ece
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1704314
Reviewed-by: Manu Cornet <manucornet@chromium.org>
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Cr-Commit-Position: refs/heads/master@{#678299}