ash: Convert ShelfDelegate to use WmShelf* instead of Shelf*

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 <memory>
 #include <string>
 
 #include "ash/common/shell_delegate.h"
 #include "base/macros.h"
 
 namespace app_list {
 class AppListPresenterDelegateFactory;
 class AppListPresenterImpl;
 }
 
 namespace keyboard {
 class KeyboardUI;
 }
 
 namespace ash {
 namespace shell {
 
-class ShelfDelegateImpl;
-
 class ShellDelegateImpl : public ShellDelegate {
  public:
   ShellDelegateImpl();
   ~ShellDelegateImpl() override;
 
   bool IsFirstRunAfterBoot() const override;
   bool IsIncognitoAllowed() const override;
   bool IsMultiProfilesEnabled() const override;
   bool IsRunningInForcedAppMode() const override;
   bool CanShowWindowForUser(WmWindow* window) const override;
@@ skipping 12 matching lines @@
   NewWindowDelegate* CreateNewWindowDelegate() override;
   MediaDelegate* CreateMediaDelegate() override;
   std::unique_ptr<PaletteDelegate> CreatePaletteDelegate() override;
   ui::MenuModel* CreateContextMenu(WmShelf* wm_shelf,
                                    const ShelfItem* item) override;
   GPUSupport* CreateGPUSupport() override;
   base::string16 GetProductName() const override;
   gfx::Image GetDeprecatedAcceleratorImage() const override;
 
  private:
-  ShelfDelegateImpl* shelf_delegate_;
+  ShelfDelegate* shelf_delegate_;
   std::unique_ptr<app_list::AppListPresenterDelegateFactory>
       app_list_presenter_delegate_factory_;
   std::unique_ptr<app_list::AppListPresenterImpl> app_list_presenter_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellDelegateImpl);
 };
 
 }  // namespace shell
 }  // namespace ash
 
 #endif  // ASH_SHELL_SHELL_DELEGATE_IMPL_H_