qtquick: Fix detecting top level geometry

For QtQuick we want the QWindow geometry. For QtWidget it just works,
as the top level widget as the same geometry as the window, unlike
QQuickItem.

Fixes issue #199

tests/tst_docks.cpp

@@ -933,10 +933,6 @@ void TestDocks::tst_hoverShowsDropIndicators()
     auto fw = floatingDockWidget->floatingWindow();
     dragFloatingWindowTo(fw, mainWindowCenterPos);
 
-#if defined(Q_OS_WIN32)
-    if (!isOffscreen())
-        QEXPECT_FAIL("", "to be fixed", Continue);
-#endif
     QCOMPARE(dock0->dptr()->frame()->dockWidgetCount(), 2);
 }
 #endif