Split the frame tree logic out of HistoryItem

Source/core/loader/FrameLoader.h

Index: Source/core/loader/FrameLoader.h
diff --git a/Source/core/loader/FrameLoader.h b/Source/core/loader/FrameLoader.h
index 18ee0f98cafcda6ae7bea34ada982fbe73e32155..0c18134b18225c6ffdce4c964e42ef7fd0a7fe50 100644
--- a/Source/core/loader/FrameLoader.h
+++ b/Source/core/loader/FrameLoader.h
@@ -81,7 +81,7 @@ public:
 
     Frame* frame() const { return m_frame; }
 
-    HistoryController* history() const { return &m_history; }
+    HistoryController* history() const { return m_history; }
 
     IconController* icon() const { return m_icon.get(); }
     MixedContentChecker* mixedContentChecker() const { return &m_mixedContentChecker; }
@@ -134,6 +134,7 @@ public:
 
     bool subframeIsLoading() const;
 
+    bool shouldTreatURLAsSameAsCurrent(const KURL&) const;
     bool shouldTreatURLAsSrcdocDocument(const KURL&) const;
 
     FrameLoadType loadType() const;
@@ -251,15 +252,14 @@ private:
     void scheduleCheckCompleted();
     void startCheckCompleteTimer();
 
-    bool shouldTreatURLAsSameAsCurrent(const KURL&) const;
-
     Frame* m_frame;
     FrameLoaderClient* m_client;
 
+    HistoryController* m_history;
+
     // FIXME: These should be OwnPtr<T> to reduce build times and simplify
     // header dependencies unless performance testing proves otherwise.
     // Some of these could be lazily created for memory savings on devices.
-    mutable HistoryController m_history;
     mutable FrameLoaderStateMachine m_stateMachine;
     OwnPtr<IconController> m_icon;
     mutable MixedContentChecker m_mixedContentChecker;