QAccessibleMenuItem: Implement QAccessibleInterface::window().

The window is required to be able to determine the correct
scale factor for the screen when High DPI scaling is active.

Change-Id: I8f776684396d055754093f62e0d33bd7e23cb52b
Task-number: QTBUG-52943
Reviewed-by: Frederik Gladhorn <frederik.gladhorn@theqtcompany.com>

src/widgets/accessible/qaccessiblemenu.cpp

@@ -225,6 +225,20 @@ QObject *QAccessibleMenuItem::object() const
     return m_action;
 }
 
+/*! \reimp */
+QWindow *QAccessibleMenuItem::window() const
+{
+    QWindow *result = Q_NULLPTR;
+    if (!m_owner.isNull()) {
+        result = m_owner->windowHandle();
+        if (!result) {
+            if (const QWidget *nativeParent = m_owner->nativeParentWidget())
+                result = nativeParent->windowHandle();
+        }
+    }
+    return result;
+}
+
 QRect QAccessibleMenuItem::rect() const
 {
     QRect rect;

src/widgets/accessible/qaccessiblemenu_p.h

@@ -108,6 +108,8 @@ public:
     QAccessibleInterface *parent() const Q_DECL_OVERRIDE;
     QAccessibleInterface *child(int index) const Q_DECL_OVERRIDE;
     QObject * object() const Q_DECL_OVERRIDE;
+    QWindow *window() const Q_DECL_OVERRIDE;
+
     QRect rect() const Q_DECL_OVERRIDE;
     QAccessible::Role role() const Q_DECL_OVERRIDE;
     void setText(QAccessible::Text t, const QString & text) Q_DECL_OVERRIDE;