Bug 1478576 - Drop GetXULWindow() check in nsBaseWidget::NotifyPresShell. r=karlt

In these days, it's common to not create a child widget, so if there is
GetXULWindow() check the notifications are not propagated to the proper pres
shell.  Even in the case there is a child widget, which means both of the parent
and the child widgets notify to the same pres shell, but NotifySizeMoveDone is
fairly cheap, and the other two notifications (SysColorChanged and ThemeChanged)
are queued and will be processed later together, so it will not be a big deal.

MozReview-Commit-ID: 2t23kVZzXgS

--HG--
extra : rebase_source : 79f8a955a70f19812373e219e2cee29f669a528e

widget/nsBaseWidget.cpp

@@ -1847,7 +1847,7 @@ nsBaseWidget::NotifyWindowMoved(int32_t aX, int32_t aY)
 void
 nsBaseWidget::NotifyPresShell(NotificationFunc aNotificationFunc)
 {
-  if (!mWidgetListener || mWidgetListener->GetXULWindow()) {
+  if (!mWidgetListener) {
     return;
   }