Update menu icons for dynamic items when we update the label.

BUG=66508
TEST=enable background mode, see wrench menu badge toggle when extensions load

Review URL: http://codereview.chromium.org/6014009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@70228 0039d316-1c4b-4281-b951-d872f2087c98