6637204: TrayIcon.displayMessage fails to show icon twice

Summary: the icon canvas should be validated to finalize its layout
Reviewed-by: ant

src/solaris/classes/sun/awt/X11/XTrayIconPeer.java

@@ -833,6 +833,7 @@ public class XTrayIconPeer implements TrayIconPeer {
                 Dimension tpSize = textPanel.getSize();
                 iconCanvas.setSize(BALLOON_ICON_WIDTH, (BALLOON_ICON_HEIGHT > tpSize.height ?
                                                         BALLOON_ICON_HEIGHT : tpSize.height));
+                iconCanvas.validate();
             }
 
             SunToolkit.executeOnEventHandlerThread(xtiPeer.target, new Runnable() {