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

net/proxy/proxy_resolver_js_bindings.h

 // 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_RESOLVER_JS_BINDINGS_H_
 #define NET_PROXY_PROXY_RESOLVER_JS_BINDINGS_H_
 #pragma once
 
 #include <string>
 
 #include "base/string16.h"
 
-class MessageLoop;
-
 namespace net {
 
 class HostResolver;
 class NetLog;
 struct ProxyResolverRequestContext;
 
 // Interface for the javascript bindings.
 class ProxyResolverJSBindings {
  public:
   ProxyResolverJSBindings() : current_request_context_(NULL) {}
@@ skipping 54 matching lines @@
     return current_request_context_;
   }
 
  private:
   ProxyResolverRequestContext* current_request_context_;
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_RESOLVER_JS_BINDINGS_H_