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 d33e5f059db996b8f78fb4dea764c59b0bd007d7..a1d1fc587cfb1b75a42fdd98be675417d6cfae7c 100644
--- a/Source/core/loader/FrameLoader.h
+++ b/Source/core/loader/FrameLoader.h
@@ -82,7 +82,7 @@ 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; }
@@ -92,7 +92,7 @@ public:
     // These functions start a load. All eventually call into loadWithNavigationAction() or loadInSameDocument().
     void load(const FrameLoadRequest&); // The entry point for non-reload, non-history loads.
     void reload(ReloadPolicy = NormalReload, const KURL& overrideURL = KURL(), const String& overrideEncoding = String());
-    void loadHistoryItem(HistoryItem*); // The entry point for all back/forward loads
+    void loadHistoryItem(HistoryItem*, HistoryLoadType = HistoryDifferentDocumentLoad); // The entry point for all back/forward loads
 
     static void reportLocalLoadFailed(Frame*, const String& url);
 
@@ -135,6 +135,7 @@ public:
 
     bool subframeIsLoading() const;
 
+    bool shouldTreatURLAsSameAsCurrent(const KURL&) const;
     bool shouldTreatURLAsSrcdocDocument(const KURL&) const;
 
     FrameLoadType loadType() const;
@@ -252,15 +253,14 @@ 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;