Remove obviously unneeded forward declarations from headers under src/{app,base,net}.

net/proxy/proxy_info.h

-// Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
+// Copyright (c) 2010 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 NET_PROXY_PROXY_INFO_H_
 #define NET_PROXY_PROXY_INFO_H_
 #pragma once
 
 #include <string>
 
 #include "net/proxy/proxy_config.h"
 #include "net/proxy/proxy_list.h"
 #include "net/proxy/proxy_retry_info.h"
 #include "net/proxy/proxy_server.h"
 
-class GURL;
-
 namespace net {
 
 // This object holds proxy information returned by ResolveProxy.
 class ProxyInfo {
  public:
   ProxyInfo();
   // Default copy-constructor and assignment operator are OK!
 
   // Uses the same proxy server as the given |proxy_info|.
   void Use(const ProxyInfo& proxy_info);
@@ skipping 80 matching lines @@
   // try. If proxy_list_ is empty, then there is nothing left to fall back to.
   ProxyList proxy_list_;
 
   // This value identifies the proxy config used to initialize this object.
   ProxyConfig::ID config_id_;
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_INFO_H_