[Extensions] Clean up the handling of ExtensionHostMsg_Request

extensions/browser/app_window/test_app_window_contents.cc

 // 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.
 
 #include "extensions/browser/app_window/test_app_window_contents.h"
 
 #include "content/public/browser/web_contents.h"
 
 namespace extensions {
 
@@ skipping 18 matching lines @@
 void TestAppWindowContents::NativeWindowClosed() {
 }
 
 void TestAppWindowContents::DispatchWindowShownForTests() const {
 }
 
 content::WebContents* TestAppWindowContents::GetWebContents() const {
   return web_contents_.get();
 }
 
+WindowController* TestAppWindowContents::GetWindowController() const {
+  return nullptr;
+}
+
 }  // namespace extensions