Enabling page visibility api in the chrome browser.

chrome/browser/ui/browser.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 CHROME_BROWSER_UI_BROWSER_H_
 #define CHROME_BROWSER_UI_BROWSER_H_
 #pragma once
 
 #include <map>
 #include <set>
@@ skipping 813 matching lines @@
   virtual bool PreHandleKeyboardEvent(const NativeWebKeyboardEvent& event,
                                         bool* is_keyboard_shortcut);
   virtual void HandleKeyboardEvent(const NativeWebKeyboardEvent& event);
   virtual void ShowRepostFormWarningDialog(TabContents* tab_contents);
   virtual void ShowCollectedCookiesDialog(TabContents* tab_contents);
   virtual bool ShouldAddNavigationToHistory(
       const history::HistoryAddPageArgs& add_page_args,
       NavigationType::Type navigation_type);
   virtual void ContentRestrictionsChanged(TabContents* source);
   virtual void WorkerCrashed();
+  virtual bool IsHidden(const TabContents* source) const OVERRIDE;
 
   // Overridden from TabContentsWrapperDelegate:
   virtual void OnDidGetApplicationInfo(TabContentsWrapper* source,
                                        int32 page_id) OVERRIDE;
   virtual void OnInstallApplication(
       TabContentsWrapper* source,
       const WebApplicationInfo& app_info) OVERRIDE;
 
   // Note that the caller is responsible for deleting |old_tab_contents|.
   virtual void SwapTabContents(TabContentsWrapper* old_tab_contents,
@@ skipping 371 matching lines @@
   // Helper which implements the TabRestoreServiceDelegate interface.
   scoped_ptr<BrowserTabRestoreServiceDelegate> tab_restore_service_delegate_;
 
   scoped_ptr<InstantController> instant_;
   scoped_ptr<InstantUnloadHandler> instant_unload_handler_;
 
   DISALLOW_COPY_AND_ASSIGN(Browser);
 };
 
 #endif  // CHROME_BROWSER_UI_BROWSER_H_