Introdcue AshWindowTreeHost and move ash/chrome specific code in WTH to ash.

ash/shell/shell_delegate_impl.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_SHELL_SHELL_DELEGATE_IMPL_H_
 #define ASH_SHELL_SHELL_DELEGATE_IMPL_H_
 
 #include <string>
 
 #include "ash/shell_delegate.h"
@@ skipping 43 matching lines @@
   virtual ash::SystemTrayDelegate* CreateSystemTrayDelegate() OVERRIDE;
   virtual ash::UserWallpaperDelegate* CreateUserWallpaperDelegate() OVERRIDE;
   virtual ash::SessionStateDelegate* CreateSessionStateDelegate() OVERRIDE;
   virtual ash::AccessibilityDelegate* CreateAccessibilityDelegate() OVERRIDE;
   virtual ash::NewWindowDelegate* CreateNewWindowDelegate() OVERRIDE;
   virtual ash::MediaDelegate* CreateMediaDelegate() OVERRIDE;
   virtual ui::MenuModel* CreateContextMenu(
       aura::Window* root_window,
       ash::ShelfItemDelegate* item_delegate,
       ash::ShelfItem* item) OVERRIDE;
-  virtual WindowTreeHostFactory* CreateWindowTreeHostFactory() OVERRIDE;
   virtual GPUSupport* CreateGPUSupport() OVERRIDE;
   virtual base::string16 GetProductName() const OVERRIDE;
 
  private:
   // Used to update Launcher. Owned by main.
   WindowWatcher* watcher_;
 
   ShelfDelegateImpl* shelf_delegate_;
   content::BrowserContext* browser_context_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellDelegateImpl);
 };
 
 }  // namespace shell
 }  // namespace ash
 
 #endif  // ASH_SHELL_SHELL_DELEGATE_IMPL_H_