Add a unique frame id and save it on HistoryItem.

Source/web/WebFrameImpl.h

Index: Source/web/WebFrameImpl.h
diff --git a/Source/web/WebFrameImpl.h b/Source/web/WebFrameImpl.h
index 37b667bb5a0b0ea44fbf2f39eafb10d8fd01b52b..ba4694d61c2285f61dd58d23fb93472369f430a1 100644
--- a/Source/web/WebFrameImpl.h
+++ b/Source/web/WebFrameImpl.h
@@ -414,7 +414,24 @@ private:
     // Returns a hit-tested VisiblePosition for the given point
     WebCore::VisiblePosition visiblePositionForWindowPoint(const WebPoint&);
 
-    FrameLoaderClientImpl m_frameLoaderClient;
+    class WebFrameInit : public WebCore::FrameInit {
+    public:
+        static PassRefPtr<WebFrameInit> create(WebFrameImpl* webFrameImpl, int64_t frameID)
+        {
+            return adoptRef(new WebFrameInit(webFrameImpl, frameID));
+        }
+
+    private:
+        WebFrameInit(WebFrameImpl* webFrameImpl, int64_t frameID)
+            : WebCore::FrameInit(frameID)
+            , m_frameLoaderClientImpl(webFrameImpl)
+        {
+            setFrameLoaderClient(&m_frameLoaderClientImpl);
+        }
+
+        FrameLoaderClientImpl m_frameLoaderClientImpl;
+    };
+    RefPtr<WebFrameInit> m_frameInit;
 
     WebFrameClient* m_client;
 
@@ -495,9 +512,6 @@ private:
     // information. Is used by PrintPage().
     OwnPtr<ChromePrintContext> m_printContext;
 
-    // The identifier of this frame.
-    long long m_embedderIdentifier;
-
     // Ensure we don't overwrite valid history data during same document loads
     // from HistoryItems
     bool m_inSameDocumentHistoryLoad;