Move the frame tree into the embedder.

Source/core/loader/EmptyClients.h

Index: Source/core/loader/EmptyClients.h
diff --git a/Source/core/loader/EmptyClients.h b/Source/core/loader/EmptyClients.h
index 7f87177b1f44ab6fa581f9d805cefa1d36eb6014..262ae0f42adadd7c419ce7f474f4b7735db022d8 100644
--- a/Source/core/loader/EmptyClients.h
+++ b/Source/core/loader/EmptyClients.h
@@ -179,6 +179,12 @@ public:
 
     virtual bool hasWebView() const OVERRIDE { return true; } // mainly for assertions
 
+    virtual Frame* parent() const OVERRIDE { return 0; }
+    virtual Frame* top() const OVERRIDE { return 0; }
+    virtual Frame* previousSibling() const OVERRIDE { return 0; }
+    virtual Frame* nextSibling() const OVERRIDE { return 0; }
+    virtual Frame* firstChild() const OVERRIDE { return 0; }
+    virtual Frame* lastChild() const OVERRIDE { return 0; }
     virtual void detachedFromParent() OVERRIDE { }
 
     virtual void dispatchWillSendRequest(DocumentLoader*, unsigned long, ResourceRequest&, const ResourceResponse&) OVERRIDE { }