content: Cleanup class/struct forward declarations

content/shell/browser/shell_url_request_context_getter.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 CONTENT_SHELL_BROWSER_SHELL_URL_REQUEST_CONTEXT_GETTER_H_
 #define CONTENT_SHELL_BROWSER_SHELL_URL_REQUEST_CONTEXT_GETTER_H_
 
 #include <memory>
 
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/single_thread_task_runner.h"
 #include "content/public/browser/browser_context.h"
 #include "net/proxy/proxy_config_service.h"
 #include "net/url_request/url_request_context_getter.h"
 #include "net/url_request/url_request_job_factory.h"
 
-namespace base {
-class MessageLoop;
-}
-
 namespace net {
 class HostResolver;
-class MappedHostResolver;
 class NetworkDelegate;
 class NetLog;
 class ProxyConfigService;
 class ProxyService;
 class URLRequestContextStorage;
 }
 
 namespace content {
 
 class ShellURLRequestContextGetter : public net::URLRequestContextGetter {
@@ skipping 36 matching lines @@
   std::unique_ptr<net::URLRequestContext> url_request_context_;
   ProtocolHandlerMap protocol_handlers_;
   URLRequestInterceptorScopedVector request_interceptors_;
 
   DISALLOW_COPY_AND_ASSIGN(ShellURLRequestContextGetter);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_SHELL_BROWSER_SHELL_URL_REQUEST_CONTEXT_GETTER_H_