extensions: Cleanup class/struct fwd declarations

extensions/browser/warning_service.h

 // Copyright (c) 2012 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 EXTENSIONS_BROWSER_WARNING_SERVICE_H_
 #define EXTENSIONS_BROWSER_WARNING_SERVICE_H_
 
 #include <set>
 #include <string>
 #include <vector>
 
 #include "base/observer_list.h"
 #include "base/scoped_observer.h"
 #include "base/threading/non_thread_safe.h"
 #include "components/keyed_service/core/keyed_service.h"
 #include "extensions/browser/extension_registry_observer.h"
 #include "extensions/browser/warning_set.h"
 
 // TODO(battre) Remove the Extension prefix.
 
 namespace content {
 class BrowserContext;
-class NotificationDetails;
-class NotificationSource;
 }
 
 namespace extensions {
 
 class ExtensionRegistry;
 
 // Manages a set of warnings caused by extensions. These warnings (e.g.
 // conflicting modifications of network requests by extensions, slow extensions,
 // etc.) trigger a warning badge in the UI and and provide means to resolve
 // them. This class must be used on the UI thread only.
@@ skipping 56 matching lines @@
   // Listen to extension unloaded notifications.
   ScopedObserver<ExtensionRegistry, ExtensionRegistryObserver>
       extension_registry_observer_;
 
   base::ObserverList<Observer> observer_list_;
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_WARNING_SERVICE_H_