Add parent pointer to NavigationEntryImpl::TreeNode.

content/browser/web_contents/web_contents_impl.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/web_contents/web_contents_impl.h"
 
 #include <stddef.h>
 
 #include <cmath>
 #include <utility>
@@ skipping 4530 matching lines @@
   // since it must come from the same document. Do not update it if a difference
   // is detected, as this indicates that |frame_entry| is not the correct one.
   ExplodedPageState exploded_state;
   if (!DecodePageState(page_state.ToEncodedData(), &exploded_state))
     return;
 
   if (exploded_state.top.document_sequence_number !=
           frame_entry->document_sequence_number() ||
       exploded_state.top.item_sequence_number !=
           frame_entry->item_sequence_number()) {
+    NOTREACHED();
     return;
   }
 
   frame_entry->set_page_state(page_state);
   controller_.NotifyEntryChanged(entry);
 }
 
 void WebContentsImpl::UpdateTitle(RenderFrameHost* render_frame_host,
                                   int32_t page_id,
                                   const base::string16& title,
@@ skipping 670 matching lines @@
   for (RenderViewHost* render_view_host : render_view_host_set)
     render_view_host->OnWebkitPreferencesChanged();
 }
 
 void WebContentsImpl::SetJavaScriptDialogManagerForTesting(
     JavaScriptDialogManager* dialog_manager) {
   dialog_manager_ = dialog_manager;
 }
 
 }  // namespace content