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

ash/test/test_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 ASH_TEST_TEST_SHELL_DELEGATE_H_
 #define ASH_TEST_TEST_SHELL_DELEGATE_H_
 
 #include <string>
 
 #include "ash/media_delegate.h"
@@ skipping 41 matching lines @@
   SystemTrayDelegate* CreateSystemTrayDelegate() override;
   UserWallpaperDelegate* CreateUserWallpaperDelegate() override;
   TestSessionStateDelegate* CreateSessionStateDelegate() override;
   AccessibilityDelegate* CreateAccessibilityDelegate() override;
   NewWindowDelegate* CreateNewWindowDelegate() override;
   MediaDelegate* CreateMediaDelegate() override;
   ui::MenuModel* CreateContextMenu(aura::Window* root,
                                    ash::ShelfItemDelegate* item_delegate,
                                    ash::ShelfItem* item) override;
   GPUSupport* CreateGPUSupport() override;
+  UserMetricsRecorderProxy* CreateUserMetricsRecorderProxy() override;
   base::string16 GetProductName() const override;
 
   int num_exit_requests() const { return num_exit_requests_; }
 
   void SetMediaCaptureState(MediaCaptureState state);
   void SetForceMaximizeOnFirstRun(bool maximize) {
     force_maximize_on_first_run_ = maximize;
   };
 
  private:
   int num_exit_requests_;
   bool multi_profiles_enabled_;
   bool force_maximize_on_first_run_;
 
   scoped_ptr<content::BrowserContext> active_browser_context_;
   scoped_ptr<app_list::AppListViewDelegate> app_list_view_delegate_;
 
   ObserverList<ash::VirtualKeyboardStateObserver> keyboard_state_observer_list_;
 
   TestSessionStateDelegate* test_session_state_delegate_;  // Not owned.
 
   DISALLOW_COPY_AND_ASSIGN(TestShellDelegate);
 };
 
 }  // namespace test
 }  // namespace ash
 
 #endif  // ASH_TEST_TEST_SHELL_DELEGATE_H_