chrome: Cleanup class/struct forward declarations

chrome/browser/extensions/blacklist.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_BLACKLIST_H_
 #define CHROME_BROWSER_EXTENSIONS_BLACKLIST_H_
 
 #include <list>
 #include <map>
 #include <memory>
@@ skipping 11 matching lines @@
 #include "content/public/browser/notification_registrar.h"
 #include "extensions/browser/blacklist_state.h"
 
 namespace content {
 class BrowserContext;
 }
 
 namespace extensions {
 
 class BlacklistStateFetcher;
-class Extension;
 class ExtensionPrefs;
 
 // The blacklist of extensions backed by safe browsing.
 class Blacklist : public KeyedService,
                   public content::NotificationObserver,
                   public base::SupportsWeakPtr<Blacklist> {
  public:
   class Observer {
    public:
     // Observes |blacklist| on construction and unobserves on destruction.
@@ skipping 114 matching lines @@
   // GetBlacklistedIDs and deleted when the callback is called from
   // OnBlacklistStateReceived.
   StateRequestsList state_requests_;
 
   DISALLOW_COPY_AND_ASSIGN(Blacklist);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_BLACKLIST_H_