8220517: Enhanced GIF support

Reviewed-by: aivanov, ssahoo, mschoene, prr

src/macosx/native/sun/awt/splashscreen/splashscreen_sys.m

 /*
- * Copyright (c) 2011, 2013, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2011, 2019, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -251,9 +251,11 @@ void
 SplashRedrawWindow(Splash * splash) {
     NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
 
+    [JNFRunLoop performOnMainThreadWaiting:YES withBlock:^(){
+        // drop the reference to the old view and image
+        [splash->window setContentView: nil];
         SplashUpdateScreenData(splash);
 
-    [JNFRunLoop performOnMainThreadWaiting:YES withBlock:^(){
         // NSDeviceRGBColorSpace vs. NSCalibratedRGBColorSpace ?
         NSBitmapImageRep * rep = [[NSBitmapImageRep alloc]
             initWithBitmapDataPlanes: (unsigned char**)&splash->screenData