Remove BackForwardClient, cleanup starting a history navigation

Source/core/loader/EmptyClients.cpp

Index: Source/core/loader/EmptyClients.cpp
diff --git a/Source/core/loader/EmptyClients.cpp b/Source/core/loader/EmptyClients.cpp
index ac150ed07bc0ecf86fc042ca47774720ef8824da..7c64dba1fb97ae2cd729a78e5173b131557abcf6 100644
--- a/Source/core/loader/EmptyClients.cpp
+++ b/Source/core/loader/EmptyClients.cpp
@@ -60,9 +60,6 @@ void fillWithEmptyClients(Page::PageClients& pageClients)
     static InspectorClient* dummyInspectorClient = adoptPtr(new EmptyInspectorClient).leakPtr();
     pageClients.inspectorClient = dummyInspectorClient;
 
-    static BackForwardClient* dummyBackForwardClient = adoptPtr(new EmptyBackForwardClient).leakPtr();
-    pageClients.backForwardClient = dummyBackForwardClient;
-
     static SpellCheckerClient* dummySpellCheckerClient = adoptPtr(new EmptySpellCheckerClient).leakPtr();
     pageClients.spellCheckerClient = dummySpellCheckerClient;