Bring QWindowPrivate::deliverUpdateRequest() back temporarily

QtWayland is using that now.

This change partly reverts commit bff59f87ba.

Task-number: QTBUG-67480
Change-Id: I36b75555baef220c80cf103226f5b8108d7a352c
Reviewed-by: Johan Helsing <johan.helsing@qt.io>

src/gui/kernel/qwindow.cpp

@@ -2358,6 +2358,12 @@ bool QWindow::event(QEvent *ev)
     return true;
 }
 
+void QWindowPrivate::deliverUpdateRequest()
+{
+    if (platformWindow)
+        platformWindow->deliverUpdateRequest();
+}
+
 /*!
     Schedules a QEvent::UpdateRequest event to be delivered to this window.
 

src/gui/kernel/qwindow_p.h

@@ -124,6 +124,8 @@ public:
     bool applyCursor();
 #endif
 
+    void deliverUpdateRequest();
+
     QPoint globalPosition() const;
 
     QWindow *topLevelWindow() const;