Gtk: fix reference counting/destruction of GtkMenu* in MenuGtk. 
Gtk: fix reference counting/destruction of GtkMenu* in MenuGtk. 

regression caused by r35404 

credit to Bryan Yeung for finding the bug 

BUG=31977, 31765, 32514, 31988
TEST=see bugs

Review URL: http://codereview.chromium.org/552044

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@36559 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser,wistoch/meego-app-browser