Clean-up coding style at apps folder

apps/app_window_registry.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 APPS_APP_WINDOW_REGISTRY_H_
 #define APPS_APP_WINDOW_REGISTRY_H_
 
 #include <list>
+#include <string>
+#include <set>
 
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/memory/singleton.h"
 #include "base/observer_list.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "ui/gfx/native_widget_types.h"
 
 namespace content {
@@ skipping 130 matching lines @@
   content::BrowserContext* context_;
   AppWindowList app_windows_;
   InspectedWindowSet inspected_windows_;
   ObserverList<Observer> observers_;
   base::Callback<void(content::DevToolsAgentHost*, bool)> devtools_callback_;
 };
 
 }  // namespace apps
 
 #endif  // APPS_APP_WINDOW_REGISTRY_H_