Add chrome.app.window API tests for items shown in shelf

chrome/browser/apps/app_browsertest_util.cc

 // Copyright 2013 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/apps/app_browsertest_util.h"
 
 #include <memory>
 #include <string>
 
 #include "base/command_line.h"
@@ skipping 276 matching lines @@
   AppWindow* app_window = GetFirstAppWindow();
   return app_window;
 }
 
 void ExperimentalPlatformAppBrowserTest::SetUpCommandLine(
     base::CommandLine* command_line) {
   PlatformAppBrowserTest::SetUpCommandLine(command_line);
   command_line->AppendSwitch(switches::kEnableExperimentalExtensionApis);
 }
 
+const gfx::ImageSkia& PlatformAppBrowserTest::GetAppIconImage(
+    AppWindow* app_window) {
+  return app_window->app_icon_image_->image_skia();
+}
+
 }  // namespace extensions