6391806: JLabel and AbstractButton's imageUpdate method should be better specified

Reviewed-by: psadhukhan, prr

Author: kumarabhi006

src/java.desktop/share/classes/javax/swing/AbstractButton.java

@@ -2146,11 +2146,12 @@ protected void init(String text, Icon icon) {
 
 
     /**
-     * This is overridden to return false if the current <code>Icon</code>'s
-     * <code>Image</code> is not equal to the
-     * passed in <code>Image</code> <code>img</code>.
+     * If the button icon for the current button state is either {@code null}
+     * or not an {@code ImageIcon} with an {@code Image} equal to the
+     * passed in {@code Image}, return {@code false}; otherwise it
+     * will delegate to the super-class.
      *
-     * @param img  the <code>Image</code> to be compared
+     * @param img  the {@code Image} to be compared
      * @param infoflags flags used to repaint the button when the image
      *          is updated and which determine how much is to be painted
      * @param x  the x coordinate

src/java.desktop/share/classes/javax/swing/JLabel.java

@@ -874,8 +874,18 @@ public void setHorizontalTextPosition(int textPosition) {
 
 
     /**
-     * This is overridden to return false if the current Icon's Image is
-     * not equal to the passed in Image <code>img</code>.
+     * If the component is not showing or either the icon or disabled
+     * icon is not an {@code ImageIcon} with an {@code Image}
+     * equal to the passed in {@code Image}, return {@code false};
+     * otherwise it will delegate to the super-class.
+     *
+     * @param img   the {@code Image} to be compared
+     * @param infoflags flags used to repaint the label when the image
+     *           is updated and which determine how much is to be painted
+     * @param x   the x coordinate
+     * @param y   the y coordinate
+     * @param w   the width
+     * @param h   the height
      *
      * @see     java.awt.image.ImageObserver
      * @see     java.awt.Component#imageUpdate(java.awt.Image, int, int, int, int, int)