Implementation for switching between recently used tabs using ctrl tilde or quoteleft.

chrome/browser/ui/tabs/mru_tab_controller.h

Index: chrome/browser/ui/tabs/mru_tab_controller.h
diff --git a/chrome/browser/ui/tabs/mru_tab_controller.h b/chrome/browser/ui/tabs/mru_tab_controller.h
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+++ b/chrome/browser/ui/tabs/mru_tab_controller.h
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+// 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.
+
+#ifndef CHROME_BROWSER_UI_TABS_MRU_TAB_CONTROLLER_H_
+#define CHROME_BROWSER_UI_TABS_MRU_TAB_CONTROLLER_H_
+
+#include <list>
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "chrome/browser/ui/tabs/tab_strip_model_observer.h"
+
+class TabContents;
+class TabStripModel;
+
+////////////////////////////////////////////////////////////////////////////////
+//
+// MRUTabController
+//
+// This is a list that manages the tabs that are in a tab strip as per the most
+// recently used priority order. This overrides TabStrip Model Observer.
+//
+////////////////////////////////////////////////////////////////////////////////
+class MRUTabController : public TabStripModelObserver {
+ public:
+  explicit MRUTabController(TabStripModel* tab_strip_model);
+  virtual ~MRUTabController();
+
+  // Retrieves the previously used tab in the mru list
+  TabContents* GetPreviousMRUTab();
+
+  // Pauses changes to the mru list.
+  void PauseStackUpdates();
+
+  // Updates the mru list by bringing currently active
+  // tab to the front of the list.
+  void CommitActiveTabChanges();
+
+  // Overridden from TabStripModelObserver:
+  virtual void TabInsertedAt(TabContents* contents,
+                             int index,
+                             bool foreground) OVERRIDE;
+  virtual void TabDetachedAt(TabContents* contents, int index) OVERRIDE;
+  virtual void ActiveTabChanged(TabContents* old_contents,
+                                TabContents* new_contents,
+                                int index,
+                                bool user_gesture) OVERRIDE;
+  virtual void TabReplacedAt(TabStripModel* tab_strip_model,
+                             TabContents* old_contents,
+                             TabContents* new_contents,
+                             int index) OVERRIDE;
+  virtual void TabStripEmpty() OVERRIDE;
+
+ private:
+  // List that maintains the tab indices in the most recently visited order
+  typedef std::list<TabContents*> TabsMRUList;
+  TabsMRUList tabs_mru_list_;
+
+  TabStripModel* tab_strip_model_;
+
+  bool can_update_stack_;
+
+  DISALLOW_COPY_AND_ASSIGN(MRUTabController);
+};
+#endif // CHROME_BROWSER_UI_TABS_MRU_TAB_CONTROLLER_H_