Bug 990812 - Allow a deeper frame message manager hierarchy than only global > window > tab
Bug 990812 - Add nsIDOMChromeWindow.getGroupMessageManager() API
Bug 990812 - Let the frame loader use a group message manager as the parent when it detects that a frame belongs to a certain group
Bug 990812 - Restrict sessionstore and browser frame scripts to tabbrowser browsers
Bug 990812 - Make a11y jsat utils handle group message managers