Added the Ash.Tab.TimeBetweenSwitchToExistingTabUserActions histogram to track time between tab swit

chrome/browser/ui/ash/chrome_shell_delegate.h

 // 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_ASH_CHROME_SHELL_DELEGATE_H_
 #define CHROME_BROWSER_UI_ASH_CHROME_SHELL_DELEGATE_H_
 
 #include <string>
 
 #include "ash/shelf/shelf_item_types.h"
@@ skipping 57 matching lines @@
   ash::SystemTrayDelegate* CreateSystemTrayDelegate() override;
   ash::UserWallpaperDelegate* CreateUserWallpaperDelegate() override;
   ash::SessionStateDelegate* CreateSessionStateDelegate() override;
   ash::AccessibilityDelegate* CreateAccessibilityDelegate() override;
   ash::NewWindowDelegate* CreateNewWindowDelegate() override;
   ash::MediaDelegate* CreateMediaDelegate() override;
   ui::MenuModel* CreateContextMenu(aura::Window* root,
                                    ash::ShelfItemDelegate* item_delegate,
                                    ash::ShelfItem* item) override;
   ash::GPUSupport* CreateGPUSupport() override;
+  ash::UserMetricsRecorderProxy* CreateUserMetricsRecorderProxy() override;
   base::string16 GetProductName() const override;
 
   // content::NotificationObserver override:
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
  private:
   void PlatformInit();
 
   static ChromeShellDelegate* instance_;
 
   content::NotificationRegistrar registrar_;
 
   ChromeLauncherController* shelf_delegate_;
 
   ObserverList<ash::VirtualKeyboardStateObserver> keyboard_state_observer_list_;
 
 #if defined(OS_CHROMEOS)
   scoped_ptr<chromeos::DisplayConfigurationObserver>
       display_configuration_observer_;
 #endif
 
   DISALLOW_COPY_AND_ASSIGN(ChromeShellDelegate);
 };
 
 #endif  // CHROME_BROWSER_UI_ASH_CHROME_SHELL_DELEGATE_H_