src/macosx/classes/sun/lwawt/LWToolkit.java

*** 520,535 ****
  
      public static void postEvent(AWTEvent event) {
          postEvent(targetToAppContext(event.getSource()), event);
      }
  
-     // use peer's back buffer to implement non-opaque windows.
-     @Override
-     public boolean needUpdateWindow() {
-         return true;
-     }
- 
      @Override
      public void grab(Window w) {
          if (w.getPeer() != null) {
              ((LWWindowPeer)w.getPeer()).grab();
          }
--- 520,529 ----