Handle app custom icon via aura::Window property.

chrome/browser/ui/apps/chrome_app_delegate.h

 // Copyright 2014 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 CHROME_BROWSER_UI_APPS_CHROME_APP_DELEGATE_H_
 #define CHROME_BROWSER_UI_APPS_CHROME_APP_DELEGATE_H_
 
 #include <memory>
 
 #include "base/callback.h"
@@ skipping 45 matching lines @@
   void RequestMediaAccessPermission(
       content::WebContents* web_contents,
       const content::MediaStreamRequest& request,
       const content::MediaResponseCallback& callback,
       const extensions::Extension* extension) override;
   bool CheckMediaAccessPermission(
       content::WebContents* web_contents,
       const GURL& security_origin,
       content::MediaStreamType type,
       const extensions::Extension* extension) override;
-  int PreferredIconSize() override;
+  int PreferredIconSize() const override;
   void SetWebContentsBlocked(content::WebContents* web_contents,
                              bool blocked) override;
   bool IsWebContentsVisible(content::WebContents* web_contents) override;
   void SetTerminatingCallback(const base::Closure& callback) override;
   void OnHide() override;
   void OnShow() override;
 
   // content::NotificationObserver:
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
   bool has_been_shown_;
   bool is_hidden_;
   std::unique_ptr<ScopedKeepAlive> keep_alive_;
   std::unique_ptr<NewWindowContentsDelegate> new_window_contents_delegate_;
   base::Closure terminating_callback_;
   content::NotificationRegistrar registrar_;
   base::WeakPtrFactory<ChromeAppDelegate> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(ChromeAppDelegate);
 };
 
 #endif  // CHROME_BROWSER_UI_APPS_CHROME_APP_DELEGATE_H_