Fix radio items in MenuGtk.
Fix radio items in MenuGtk.

Suppose there are three radio items A, B, C, and A is now being
checked. If you click C, commands associated with A and C are both
executed. This is because A also receives the "activate" signal,
before C receives it.

BUG=30450
TEST=try; manually with gdb with the steps described in crbug.com/30450.

Review URL: http://codereview.chromium.org/506010

git-svn-id: dd90618784b6a4b323ea0c23a071cb1c9e6f2ac7@34647 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