Make the update_url key allowed for themes.
Make the update_url key allowed for themes.

Review URL: http://codereview.chromium.org/160426

git-svn-id: http://src.chromium.org/svn/trunk/src@22118 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: cf8bd2e25f2be996e904df5b6b5b3ede5741316e
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