Use Ash's ShelfWindowWatcher for app panel windows.

ash/mus/bridge/wm_window_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_BRIDGE_WM_WINDOW_MUS_H_
 #define ASH_MUS_BRIDGE_WM_WINDOW_MUS_H_
 
 #include <memory>
 
 #include "ash/common/wm_window.h"
@@ skipping 134 matching lines @@
   float GetTargetOpacity() const override;
   gfx::Rect GetMinimizeAnimationTargetBoundsInScreen() const override;
   void SetTransform(const gfx::Transform& transform) override;
   gfx::Transform GetTargetTransform() const override;
   bool IsSystemModal() const override;
   bool GetBoolProperty(WmWindowProperty key) override;
   SkColor GetColorProperty(WmWindowProperty key) override;
   void SetColorProperty(WmWindowProperty key, SkColor value) override;
   int GetIntProperty(WmWindowProperty key) override;
   void SetIntProperty(WmWindowProperty key, int value) override;
+  gfx::ImageSkia GetWindowIcon() override;
+  gfx::ImageSkia GetAppIcon() override;
   const wm::WindowState* GetWindowState() const override;
   WmWindow* GetToplevelWindow() override;
   WmWindow* GetToplevelWindowForFocus() override;
   void SetParentUsingContext(WmWindow* context,
                              const gfx::Rect& screen_bounds) override;
   void AddChild(WmWindow* window) override;
   void RemoveChild(WmWindow* child) override;
   const WmWindow* GetParent() const override;
   const WmWindow* GetTransientParent() const override;
   std::vector<WmWindow*> GetTransientChildren() override;
@@ skipping 145 matching lines @@
 
   bool locked_to_root_ = false;
 
   DISALLOW_COPY_AND_ASSIGN(WmWindowMus);
 };
 
 }  // namespace mus
 }  // namespace ash
 
 #endif  // ASH_MUS_BRIDGE_WM_WINDOW_MUS_H_