back out 376077, too problematic for beta 2.

widget/src/cocoa/nsChildView.mm

@@ -4106,11 +4106,7 @@ static BOOL keyUpAlreadySentKeyDown = NO;
   ConvertCocoaKeyEventToMacEvent(theEvent, macEvent);
   geckoEvent.nativeMsg = &macEvent;
 
-  mGeckoChild->DispatchWindowEvent(geckoEvent);
-
-  // We always return YES here because we can't know for sure if Gecko
-  // handled the event, even with the return value for the event dispatch.
-  return YES;
+  return (BOOL)mGeckoChild->DispatchWindowEvent(geckoEvent);
 }