force undo commands to be updated (bug 183133); r=sfraser, sr=kin

editor/ui/composer/content/editor.js

@@ -398,7 +398,9 @@ var gEditorDocumentObserver =
 
       case "cmd_bold":
         // Update all style items
+        // cmd_bold is a proxy; see EditorSharedStartup (above) for details
         window.updateCommands("style");
+        window.updateCommands("undo");
         break;
     }
   }