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

net/http/http_auth_sspi_win.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.
 
 // This file contains common routines used by NTLM and Negotiate authentication
 // using the SSPI API on Windows.
 
 #ifndef NET_HTTP_HTTP_AUTH_SSPI_WIN_H_
 #define NET_HTTP_HTTP_AUTH_SSPI_WIN_H_
 #pragma once
 
 // security.h needs to be included for CredHandle. Unfortunately CredHandle
 // is a typedef and can't be forward declared.
 #define SECURITY_WIN32 1
 #include <windows.h>
 #include <security.h>
 
 #include <string>
 
 #include "base/string16.h"
 #include "net/http/http_auth.h"
 
 namespace net {
 
-struct HttpRequestInfo;
-class ProxyInfo;
-
 // SSPILibrary is introduced so unit tests can mock the calls to Windows' SSPI
 // implementation. The default implementation simply passes the arguments on to
 // the SSPI implementation provided by Secur32.dll.
 // NOTE(cbentzel): I considered replacing the Secur32.dll with a mock DLL, but
 // decided that it wasn't worth the effort as this is unlikely to be performance
 // sensitive code.
 class SSPILibrary {
  public:
   virtual ~SSPILibrary() {}
 
@@ skipping 107 matching lines @@
 // If the return value is ERR_UNEXPECTED, there was an unanticipated problem
 // in the underlying SSPI call. The details are logged, and |*max_token_length|
 // is not changed.
 int DetermineMaxTokenLength(SSPILibrary* library,
                             const std::wstring& package,
                             ULONG* max_token_length);
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_AUTH_SSPI_WIN_H_