Remove an invalid DCHECK. If we are closing the browser and the beforeunload handler hangs, then is_waiting_for_unload_ack will be true here.
Remove an invalid DCHECK. If we are closing the browser and
the beforeunload handler hangs, then is_waiting_for_unload_ack
will be true here.

git-svn-id: http://src.chromium.org/svn/trunk/src@719 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 1b667bb57f011eb003ac733370f9579e583667a2
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