macOS: Move setMask call out of recreateWindowIfNeeded

It semantically applies during platform window initialization, and
doesn't depend on the logic of choosing an appropriate NSWindow class.

Pick-to: 6.5
Change-Id: Ia24a2deafc78ed4c79df766b6372ad64de2d0dde
Reviewed-by: Doris Verria <doris.verria@qt.io>

src/plugins/platforms/cocoa/qcocoawindow.mm

@@ -147,6 +147,8 @@ void QCocoaWindow::initialize()
 
     recreateWindowIfNeeded();
 
+    setMask(QHighDpi::toNativeLocalRegion(window()->mask(), window()));
+
     m_initialized = true;
 }
 
@@ -1530,8 +1532,6 @@ void QCocoaWindow::recreateWindowIfNeeded()
         [parentCocoaWindow->m_view addSubview:m_view];
         [m_view setHidden:!window()->isVisible()];
     }
-
-    setMask(QHighDpi::toNativeLocalRegion(window()->mask(), window()));
 }
 
 void QCocoaWindow::requestUpdate()