Handle app custom icon via aura::Window property.

extensions/browser/app_window/app_window_registry.h

Index: extensions/browser/app_window/app_window_registry.h
diff --git a/extensions/browser/app_window/app_window_registry.h b/extensions/browser/app_window/app_window_registry.h
index 799c4f643a483e1fe33e310fa4c121b9bb2253f6..e63b48b1cdde27945ef5d8d4cfe9f8771ed94b6d 100644
--- a/extensions/browser/app_window/app_window_registry.h
+++ b/extensions/browser/app_window/app_window_registry.h
@@ -37,8 +37,6 @@ class AppWindowRegistry : public KeyedService,
    public:
     // Called just after a app window was added.
     virtual void OnAppWindowAdded(AppWindow* app_window);
-    // Called when the window icon changes.
-    virtual void OnAppWindowIconChanged(AppWindow* app_window);
     // Called just after a app window was removed.
     virtual void OnAppWindowRemoved(AppWindow* app_window);
     // Called just after a app window was hidden. This is different from
@@ -67,7 +65,6 @@ class AppWindowRegistry : public KeyedService,
   static AppWindowRegistry* Get(content::BrowserContext* context);
 
   void AddAppWindow(AppWindow* app_window);
-  void AppWindowIconChanged(AppWindow* app_window);
   // Called by |app_window| when it is activated.
   void AppWindowActivated(AppWindow* app_window);
   void AppWindowHidden(AppWindow* app_window);