Fixes possible crash in menu code. If after dropping you quickly right click the mouse we would crash.
Fixes possible crash in menu code. If after dropping you quickly right
click the mouse we would crash.

BUG=4047
TEST=see bug

Review URL: http://codereview.chromium.org/9346

git-svn-id: http://src.chromium.org/svn/trunk/src@4647 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: d9bbf176154f2f950953f1e1ae1ba1cba15d8a91
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