Revert 225253 "Don't leave renderer process frozen when cancelin..."

Led to http://crbug.com/300129.

> Don't leave renderer process frozen when canceling JavaScript dialogs.
> 
> BUG=297289
> TEST=See bug for repro steps.
> R=avi@chromium.org, sky@chromium.org
> 
> Review URL: https://codereview.chromium.org/24436003

TBR=creis@chromium.org

Review URL: https://codereview.chromium.org/25062004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225808 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225808