Bug 1454440 - Focus the window directly instead of using commandDispatcher in the mac Window menu;r=Gijs

This fixes the Window menu with top-level HTML windows, which don't have `commandDispatcher`
defined on the document.

MozReview-Commit-ID: I7T1LrMf8Ik

--HG--
extra : rebase_source : e2ca69690cfa11716a17dc0ce268a7c4a4aa7e2b

toolkit/content/macWindowMenu.js

@@ -21,7 +21,7 @@ function macWindowMenuDidShow() {
       if (win.windowState == window.STATE_MINIMIZED) {
         win.restore();
       }
-      win.document.commandDispatcher.focusedWindow.focus();
+      win.focus();
     });
     frag.appendChild(item);
   }