8232744: j.awt.Window::setShape(Shape) paints visible artifacts outsi…

…de of the given shape

Reviewed-by: prr

src/java.desktop/share/classes/java/awt/Window.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1995, 2019, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1995, 2020, 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
@@ -134,6 +134,11 @@
  * geometry in order to place and size the {@code Window} in a way
  * that more closely matches the desktop settings.
  * <p>
+ * Visual effects such as halos, shadows, motion effects and animations may be
+ * applied to the window by the desktop window management system. These are
+ * outside the knowledge and control of the AWT and so for the purposes of this
+ * specification are not considered part of the top-level window.
+ * <p>
  * Due to the asynchronous nature of native event handling, the results
  * returned by {@code getBounds}, {@code getLocation},
  * {@code getLocationOnScreen}, and {@code getSize} might not