Add browser back accelerator to app list

Changes:
Treat browser back as esc key to navigate back in app list.

BUG=819668

Change-Id: Iccccfe8b424570643c851a73d191e86f66271ced
Reviewed-on: https://chromium-review.googlesource.com/978546
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Weidong Guo <weidongg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#545576}
1 file changed