Add isWindow type to QObject

(cherry picked from commit 77f08730b4cdb23b43471b2b29ece59e159103d7)

src/corelib/kernel/qobject.cpp

@@ -157,6 +157,7 @@ QObjectPrivate::QObjectPrivate(int version)
 #endif
     metaObject = 0;
     hasGuards = false;
+    isWindow = false;
 }
 
 QObjectPrivate::~QObjectPrivate()

src/corelib/kernel/qobject.h

@@ -102,7 +102,8 @@ public:
     uint inEventHandler : 1; //only used if QT_JAMBI_BUILD
     uint inThreadChangeEvent : 1;
     uint hasGuards : 1; //true iff there is one or more QPointer attached to this object
-    uint unused : 22;
+    uint isWindow : 1; //for QWindow
+    uint unused : 21;
     int postedEvents;
     QMetaObject *metaObject; // assert dynamic
 };
@@ -144,6 +145,7 @@ public:
     void setObjectName(const QString &name);
 
     inline bool isWidgetType() const { return d_ptr->isWidget; }
+    inline bool isWindowType() const { return d_ptr->isWindow; }
 
     inline bool signalsBlocked() const { return d_ptr->blockSig; }
     bool blockSignals(bool b);

src/gui/kernel/qwindow_qpa.cpp

@@ -63,7 +63,7 @@ public:
         , glContext(0)
         , widget(0)
     {
-
+        isWindow = true;
     }
 
     ~QWindowPrivate()