Clear any open dialogs when the renderer process goes away.

BUG=343625
TEST=See bug for repro steps.
R=darin@chromium.org

Review URL: https://codereview.chromium.org/177123002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253006 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253006