Make DOMWindowProperty a thin wrapper of ContextLifecycleObserver

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

Index: third_party/WebKit/Source/core/frame/DOMWindowProperty.h
diff --git a/third_party/WebKit/Source/core/frame/DOMWindowProperty.h b/third_party/WebKit/Source/core/frame/DOMWindowProperty.h
index 06257b303bf8770ac3782f34286aefc9ef15ffda..5bdb1207f7927e67cabb85d116896063b0b0400b 100644
--- a/third_party/WebKit/Source/core/frame/DOMWindowProperty.h
+++ b/third_party/WebKit/Source/core/frame/DOMWindowProperty.h
@@ -27,24 +27,18 @@
 #define DOMWindowProperty_h
 
 #include "core/CoreExport.h"
+#include "core/dom/ContextLifecycleObserver.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class LocalFrame;
 
-class CORE_EXPORT DOMWindowProperty : public GarbageCollectedMixin {
+// TODO(haraken): Deprecate DOMWindowProperty.
+class CORE_EXPORT DOMWindowProperty : public ContextLifecycleObserver {
  public:
   explicit DOMWindowProperty(LocalFrame*);
-
-  virtual void frameDestroyed();
-
-  LocalFrame* frame() const { return m_frame; }
-
-  DECLARE_VIRTUAL_TRACE();
-
- private:
-  Member<LocalFrame> m_frame;
+  LocalFrame* frame() const;
 };
 
 }  // namespace blink