Added notification when user presses backspace to use new shortcut.

chrome/browser/ui/browser_window.h

 // Copyright 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_BROWSER_WINDOW_H_
 #define CHROME_BROWSER_UI_BROWSER_WINDOW_H_
 
 #include "base/callback_forward.h"
 #include "build/build_config.h"
 #include "chrome/browser/lifetime/browser_close_manager.h"
@@ skipping 128 matching lines @@
   // + or - in the app menu to change zoom).
   virtual void ZoomChangedForActiveTab(bool can_show_bubble) = 0;
 
   // Windows and GTK remove the top controls in fullscreen, but Mac and Ash
   // keep the controls in a slide-down panel.
   virtual bool ShouldHideUIForFullscreen() const = 0;
 
   // Returns true if the fullscreen bubble is visible.
   virtual bool IsFullscreenBubbleVisible() const = 0;
 
+  // Shows a notice teaching the user the new shortcut for going Back or
+  // Forward.
+  virtual void ShowNewBackShortcutBubble(bool forward) = 0;
+
   // Returns the size of WebContents in the browser. This may be called before
   // the TabStripModel has an active tab.
   virtual gfx::Size GetContentsSize() const = 0;
 
   // Returns the location bar.
   virtual LocationBar* GetLocationBar() const = 0;
 
   // Tries to focus the location bar.  Clears the window focus (to avoid
   // inconsistent state) if this fails.
   virtual void SetFocusToLocationBar(bool select_all) = 0;
@@ skipping 219 matching lines @@
   // currently resides in.
   virtual std::string GetWorkspace() const = 0;
 
  protected:
   friend class BrowserCloseManager;
   friend class BrowserView;
   virtual void DestroyBrowser() = 0;
 };
 
 #endif  // CHROME_BROWSER_UI_BROWSER_WINDOW_H_