chromeos: Remove Backspace accelerator.
chromeos: Remove Backspace accelerator.

The people with whom I spoke (ben, glen, alcor) think that
we should expose a better method for going back in the
browser history and are okay with removing this for now.

BUG=none
TEST=none

Review URL: http://codereview.chromium.org/2871026

git-svn-id: http://src.chromium.org/svn/trunk/src@50909 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 0d4fee9d6b8393c009bfef69bca4ad047b7b2ccc
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser