Remove BackForwardClient, cleanup starting a history navigation

Source/core/testing/DummyPageHolder.cpp

 /*
  * Copyright (c) 2013, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 42 matching lines @@
     PassOwnPtr<FrameLoaderClient> frameLoaderClient)
 {
     if (!pageClients) {
         fillWithEmptyClients(m_pageClients);
     } else {
         m_pageClients.chromeClient = pageClients->chromeClient;
         m_pageClients.contextMenuClient = pageClients->contextMenuClient;
         m_pageClients.editorClient = pageClients->editorClient;
         m_pageClients.dragClient = pageClients->dragClient;
         m_pageClients.inspectorClient = pageClients->inspectorClient;
-        m_pageClients.backForwardClient = pageClients->backForwardClient;
         m_pageClients.spellCheckerClient = pageClients->spellCheckerClient;
         m_pageClients.storageClient = pageClients->storageClient;
     }
     m_page = adoptPtrWillBeNoop(new Page(m_pageClients));
     Settings& settings = m_page->settings();
     // FIXME: http://crbug.com/363843. This needs to find a better way to
     // not create graphics layers.
     settings.setAcceleratedCompositingEnabled(false);
 
     m_frameLoaderClient = frameLoaderClient;
@@ skipping 30 matching lines @@
 {
     return *m_frame->view();
 }
 
 Document& DummyPageHolder::document() const
 {
     return *m_frame->domWindow()->document();
 }
 
 } // namespace blink