Null out LocalDOMWindow::m_frame on navigation.

third_party/WebKit/Source/core/frame/LocalDOMWindow.h

 /*
  * Copyright (C) 2006, 2007, 2009, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 205 matching lines @@
     // LocalFrame*.
     class WindowFrameObserver final : public NoBaseWillBeGarbageCollected<WindowFrameObserver>, public LocalFrameLifecycleObserver {
         WTF_MAKE_FAST_ALLOCATED_WILL_BE_REMOVED(WindowFrameObserver);
         WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(WindowFrameObserver);
         DECLARE_EMPTY_VIRTUAL_DESTRUCTOR_WILL_BE_REMOVED(WindowFrameObserver);
     public:
         static PassOwnPtrWillBeRawPtr<WindowFrameObserver> create(LocalDOMWindow*, LocalFrame&);
 
         DECLARE_VIRTUAL_TRACE();
 
-    private:
-        WindowFrameObserver(LocalDOMWindow*, LocalFrame&);
-
         // LocalFrameLifecycleObserver overrides:
         void willDetachFrameHost() override;
         void contextDestroyed() override;
 
+    private:
+        WindowFrameObserver(LocalDOMWindow*, LocalFrame&);
+
         RawPtrWillBeMember<LocalDOMWindow> m_window;
     };
     friend WTF::OwnedPtrDeleter<WindowFrameObserver>;
 
     explicit LocalDOMWindow(LocalFrame&);
     void dispose();
 
     Page* page();
 
     void clearDocument();
@@ skipping 43 matching lines @@
 }
 
 inline String LocalDOMWindow::defaultStatus() const
 {
     return m_defaultStatus;
 }
 
 } // namespace blink
 
 #endif // LocalDOMWindow_h