Prevent a crash when a popup menu is closing.
Prevent a crash when a popup menu is closing.

See http://codereview.chromium.org/13214

Review URL: http://codereview.chromium.org/14884

git-svn-id: http://src.chromium.org/svn/trunk/src@7315 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 50cf9086e8b6338621a6eba11bbd45a83207f7d2
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