Bug 1534935: Fix non-nsView ShouldNotBeVisible(). r=jmathies

The comment was correct, the base impl should always return false as we don't have an opinion about visibility.

Differential Revision: https://phabricator.services.mozilla.com/D23598

--HG--
extra : moz-landing-system : lando

widget/nsIWidgetListener.cpp

@@ -72,7 +72,7 @@ void nsIWidgetListener::RequestRepaint() {}
 
 bool nsIWidgetListener::ShouldNotBeVisible() {
   // Returns false to assume that nothing should happen in most cases.
-  return true;
+  return false;
 }
 
 nsEventStatus nsIWidgetListener::HandleEvent(WidgetGUIEvent* aEvent,