ios: Cleanup class/struct forward declarations

ios/chrome/browser/signin/signin_client_impl.h

 // Copyright 2015 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 IOS_CHROME_BROWSER_SIGNIN_SIGNIN_CLIENT_IMPL_H_
 #define IOS_CHROME_BROWSER_SIGNIN_SIGNIN_CLIENT_IMPL_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "components/signin/core/browser/signin_client.h"
 #include "components/signin/core/browser/signin_error_controller.h"
 #include "google_apis/gaia/gaia_oauth_client.h"
 #include "google_apis/gaia/oauth2_token_service.h"
 #include "net/base/network_change_notifier.h"
 
-namespace content_settings {
-class CookieSettings;
-}
-
 namespace ios {
 class ChromeBrowserState;
 }
 
 class SigninClientImpl
     : public SigninClient,
       public net::NetworkChangeNotifier::NetworkChangeObserver,
       public SigninErrorController::Observer,
       public gaia::GaiaOAuthClient::Delegate,
       public OAuth2TokenService::Consumer {
@@ skipping 73 matching lines @@
   SigninErrorController* signin_error_controller_;
   std::list<base::Closure> delayed_callbacks_;
 
   std::unique_ptr<gaia::GaiaOAuthClient> oauth_client_;
   std::unique_ptr<OAuth2TokenService::Request> oauth_request_;
 
   DISALLOW_COPY_AND_ASSIGN(SigninClientImpl);
 };
 
 #endif  // IOS_CHROME_BROWSER_SIGNIN_SIGNIN_CLIENT_IMPL_H_