Handle app custom icon via aura::Window property.

chrome/browser/ui/ash/launcher/extension_app_window_launcher_item_controller.cc

 // 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.
 
 #include "chrome/browser/ui/ash/launcher/extension_app_window_launcher_item_controller.h"
 
 #include "ash/public/cpp/shelf_item_delegate.h"
 #include "ash/wm/window_state.h"
 #include "ash/wm/window_util.h"
 #include "base/memory/ptr_util.h"
@@ skipping 40 matching lines @@
 
     ash::mojom::MenuItemPtr item(ash::mojom::MenuItem::New());
     item->command_id = window_index;
     item->label = app_window->GetTitle();
 
     // Use the app's web contents favicon, or the app window's icon.
     favicon::FaviconDriver* favicon_driver =
         favicon::ContentFaviconDriver::FromWebContents(
             app_window->web_contents());
     gfx::Image icon = favicon_driver->GetFavicon();
-    if (icon.IsEmpty())
-      icon = app_window->app_icon();
+    if (icon.IsEmpty()) {
+      const gfx::ImageSkia* app_icon = nullptr;
+      if (app_window->GetNativeWindow()) {
+        app_icon = app_window->GetNativeWindow()->GetProperty(
+            aura::client::kAppIconKey);
+      }
+      if (app_icon && !app_icon->isNull())
+        icon = gfx::Image(*app_icon);
+    }
     if (!icon.IsEmpty())
       item->image = *icon.ToSkBitmap();
     items.push_back(std::move(item));
     ++window_index;
   }
   return items;
 }
 
 void ExtensionAppWindowLauncherItemController::ExecuteCommand(
     uint32_t command_id,
     int32_t event_flags) {
   ChromeLauncherController::instance()->ActivateShellApp(app_id(), command_id);
 }