Add generic PaletteDelegate code.

ash/mus/shell_delegate_mus.h

 // Copyright 2016 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_MUS_SHELL_DELEGATE_MUS_H_
 #define ASH_MUS_SHELL_DELEGATE_MUS_H_
 
 #include <memory>
 
 #include "ash/common/shell_delegate.h"
@@ skipping 28 matching lines @@
   keyboard::KeyboardUI* CreateKeyboardUI() override;
   void OpenUrlFromArc(const GURL& url) override;
   app_list::AppListPresenter* GetAppListPresenter() override;
   ShelfDelegate* CreateShelfDelegate(ShelfModel* model) override;
   SystemTrayDelegate* CreateSystemTrayDelegate() override;
   UserWallpaperDelegate* CreateUserWallpaperDelegate() override;
   SessionStateDelegate* CreateSessionStateDelegate() override;
   AccessibilityDelegate* CreateAccessibilityDelegate() override;
   NewWindowDelegate* CreateNewWindowDelegate() override;
   MediaDelegate* CreateMediaDelegate() override;
+  std::unique_ptr<PaletteDelegate> CreatePaletteDelegate() override;
   std::unique_ptr<PointerWatcherDelegate> CreatePointerWatcherDelegate()
       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:
   std::unique_ptr<app_list::AppListPresenter> app_list_presenter_;
   shell::Connector* connector_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellDelegateMus);
 };
 
 }  // namespace ash
 
 #endif  // ASH_MUS_SHELL_DELEGATE_MUS_H_