chromecast: Cleanup class/struct fwd declarations

chromecast/net/network_change_notifier_factory_cast.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 CHROMECAST_NET_NETWORK_CHANGE_NOTIFIER_FACTORY_CAST_H_
 #define CHROMECAST_NET_NETWORK_CHANGE_NOTIFIER_FACTORY_CAST_H_
 
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "net/base/network_change_notifier_factory.h"
 
 namespace chromecast {
 
-class NetworkChangeNotifierCast;
-
 class NetworkChangeNotifierFactoryCast
     : public net::NetworkChangeNotifierFactory {
  public:
   NetworkChangeNotifierFactoryCast() {}
   ~NetworkChangeNotifierFactoryCast() override;
 
   // net::NetworkChangeNotifierFactory implementation:
   net::NetworkChangeNotifier* CreateInstance() override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(NetworkChangeNotifierFactoryCast);
 };
 
 }  // namespace chromecast
 
 #endif  // CHROMECAST_NET_NETWORK_CHANGE_NOTIFIER_FACTORY_CAST_H_