--- qtbase/src/widgets/widgets/qdockwidget.h	2016-06-10 09:48:56.000000000 +0300
+++ qtbase/src/widgets/widgets/qdockwidget.h	2016-09-09 15:18:28.355926600 +0300
@@ -77,9 +77,10 @@
         DockWidgetMovable     = 0x02,
         DockWidgetFloatable   = 0x04,
         DockWidgetVerticalTitleBar = 0x08,
+        DockWidgetUndockRestoreSize = 0x10,
 
-        DockWidgetFeatureMask = 0x0f,
-        AllDockWidgetFeatures = DockWidgetClosable|DockWidgetMovable|DockWidgetFloatable, // ### Qt 6: remove
+        DockWidgetFeatureMask = 0x1f,
+        AllDockWidgetFeatures = DockWidgetClosable|DockWidgetMovable|DockWidgetFloatable|DockWidgetUndockRestoreSize, // ### Qt 6: remove
         NoDockWidgetFeatures  = 0x00,
 
         Reserved              = 0xff
@@ -101,6 +102,9 @@
     inline bool isAreaAllowed(Qt::DockWidgetArea area) const
     { return (allowedAreas() & area) == area; }
 
+    QSize undockedSize() const;
+    void setUndockedSize(const QSize &size);
+
 #ifndef QT_NO_ACTION
     QAction *toggleViewAction() const;
 #endif