Bugfix for Hover which is visible above other application windows. #2534

This patch is fixing the problem, where the HoverManagers listeners are
deregistered but the hover is still visibile on top. This happens when
the hover was sticky eclipse was minimized and put back on foreground
after it. In that case the listeners are already deregistered and there
is no chance to react at all. So for this case the visibility has to be
set explicitly when the close is going to stop.

org.eclipse.xtext.xbase.ui/src/org/eclipse/xtext/xbase/ui/hover/XbaseInformationControl.java

@@ -514,15 +514,16 @@ public static boolean isAvailable(Composite parent) {
 	@Override
 	public void setVisible(boolean visible) {
 		Shell shell = getShell();
-		if (shell.isVisible() == visible)
-			return;
 
 		if (!visible) {
 			super.setVisible(false);
 			setInput(null);
 			startDisposeTimeout(shell.getDisplay());
 			return;
 		}
+
+		if (shell.isVisible() == visible)
+			return;
 
 		/*
 		 * The Browser widget flickers when made visible while it is not completely loaded.