Fix submenu leak in menu2.  Added "destroy" signal handler to delete menu2 only when the native gtk widget  gets destroyed first.
Fix submenu leak in menu2.
 Added "destroy" signal handler to delete menu2 only when the native gtk widget
 gets destroyed first.

BUG=33475
TEST=chromeos valgrind tests passes without suppression.

Review URL: http://codereview.chromium.org/557058

git-svn-id: http://src.chromium.org/svn/trunk/src@37888 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 63705aecc30719db0e8318abc85930b5587fa406
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