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

ash/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_SHELL_DELEGATE_H_
 #define ASH_SHELL_DELEGATE_H_
 
 #include <string>
 
 #include "ash/ash_export.h"
@@ skipping 24 matching lines @@
 
 namespace keyboard {
 class KeyboardControllerProxy;
 }
 
 namespace ash {
 
 class AccessibilityDelegate;
 class MediaDelegate;
 class NewWindowDelegate;
-class WindowTreeHostFactory;
 class SessionStateDelegate;
 class ShelfDelegate;
 class ShelfItemDelegate;
 class ShelfModel;
 class SystemTrayDelegate;
 class UserWallpaperDelegate;
 struct ShelfItem;
 
 class ASH_EXPORT VirtualKeyboardStateObserver {
  public:
@@ skipping 83 matching lines @@
   virtual MediaDelegate* CreateMediaDelegate() = 0;
 
   // Creates a menu model of the context for the |root_window|.
   // When a ContextMenu is used for an item created by ShelfWindowWatcher,
   // passes its ShelfItemDelegate and ShelfItem.
   virtual ui::MenuModel* CreateContextMenu(
       aura::Window* root_window,
       ash::ShelfItemDelegate* item_delegate,
       ash::ShelfItem* item) = 0;
 
-  // Creates a root window host factory. Shell takes ownership of the returned
-  // value.
-  virtual WindowTreeHostFactory* CreateWindowTreeHostFactory() = 0;
-
   // Creates a GPU support object. Shell takes ownership of the object.
   virtual GPUSupport* CreateGPUSupport() = 0;
 
   // Get the product name.
   virtual base::string16 GetProductName() const = 0;
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELL_DELEGATE_H_