Additional fixes for prerender/instant + browsing history.

content/browser/tab_contents/tab_contents.h

 // Copyright (c) 2011 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.
 
 #ifndef CONTENT_BROWSER_TAB_CONTENTS_TAB_CONTENTS_H_
 #define CONTENT_BROWSER_TAB_CONTENTS_TAB_CONTENTS_H_
 #pragma once
 
 #include <deque>
 #include <map>
@@ skipping 608 matching lines @@
 
   // Causes the TabContents to navigate in the right renderer to |entry|, which
   // must be already part of the entries in the navigation controller.
   // This does not change the NavigationController state.
   bool NavigateToEntry(const NavigationEntry& entry,
                        NavigationController::ReloadType reload_type);
 
   // Sets the history for this tab_contents to |history_length| entries, and
   // moves the current page_id to the last entry in the list if it's valid.
   // This is mainly used when a prerendered page is swapped into the current
-  // tab.
-  void SetHistoryLengthAndClear(int history_length);
-
+  // tab. The method is virtual for testing.
+  virtual void SetHistoryLengthAndPrune(const SiteInstance* site_instance,
+                                        int merge_history_length,
+                                        int32 minimum_page_id);
 
   // Misc non-view stuff -------------------------------------------------------
 
   // Helper functions for sending notifications.
   void NotifySwapped();
   void NotifyConnected();
   void NotifyDisconnected();
 
   // RenderViewHostDelegate ----------------------------------------------------
 
@@ skipping 223 matching lines @@
   ObserverList<TabContentsObserver> observers_;
 
   // Content restrictions, used to disable print/copy etc based on content's
   // (full-page plugins for now only) permissions.
   int content_restrictions_;
 
   DISALLOW_COPY_AND_ASSIGN(TabContents);
 };
 
 #endif  // CONTENT_BROWSER_TAB_CONTENTS_TAB_CONTENTS_H_