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

net/http/http_auth_handler_mock.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_HTTP_HTTP_AUTH_HANDLER_MOCK_H_
 #define NET_HTTP_HTTP_AUTH_HANDLER_MOCK_H_
 #pragma once
 
 #include <string>
 
 #include "base/string16.h"
 #include "base/task.h"
 #include "googleurl/src/gurl.h"
 #include "net/http/http_auth_handler.h"
 #include "net/http/http_auth_handler_factory.h"
 
 namespace net {
 
+class HostResolver;
+
 // MockAuthHandler is used in tests to reliably trigger edge cases.
 class HttpAuthHandlerMock : public HttpAuthHandler {
  public:
   enum Resolve {
     RESOLVE_INIT,
     RESOLVE_SKIP,
     RESOLVE_SYNC,
     RESOLVE_ASYNC,
     RESOLVE_TESTED,
   };
@@ skipping 69 matching lines @@
   int generate_rv_;
   std::string* auth_token_;
   bool first_round_;
   bool connection_based_;
   GURL request_url_;
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_AUTH_HANDLER_MOCK_H_