Fix crash when shutting down xmpp connection.
Fix crash when shutting down xmpp connection.

BUG=None
TEST=Client doesn't crash when shuttind down connection.

Review URL: http://codereview.chromium.org/5604002

git-svn-id: http://src.chromium.org/svn/trunk/src@68113 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 5048a73324648461287e7661eec18c3b50275f26
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