Remove some illegal enum forward declarations

sandbox/win/src/named_pipe_policy.h

 // Copyright (c) 2006-2008 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 SANDBOX_SRC_NAMED_PIPE_POLICY_H__
 #define SANDBOX_SRC_NAMED_PIPE_POLICY_H__
 
 #include <string>
 
 #include "base/strings/string16.h"
 #include "sandbox/win/src/crosscall_server.h"
 #include "sandbox/win/src/policy_low_level.h"
 #include "sandbox/win/src/sandbox_policy.h"
 
 namespace sandbox {
 
-enum EvalResult;
-
 // This class centralizes most of the knowledge related to named pipe creation.
 class NamedPipePolicy {
  public:
   // Creates the required low-level policy rules to evaluate a high-level.
   // policy rule for named pipe creation
   // 'name' is the named pipe to be created
   // 'semantics' is the desired semantics.
   // 'policy' is the policy generator to which the rules are going to be added.
   static bool GenerateRules(const wchar_t* name,
                             TargetPolicy::Semantics semantics,
                             LowLevelPolicy* policy);
 
   // Processes a 'CreateNamedPipeW()' request from the target.
   static DWORD CreateNamedPipeAction(EvalResult eval_result,
                                      const ClientInfo& client_info,
                                      const base::string16 &name,
                                      DWORD open_mode, DWORD pipe_mode,
                                      DWORD max_instances,
                                      DWORD out_buffer_size,
                                      DWORD in_buffer_size,
                                      DWORD default_timeout, HANDLE* pipe);
 };
 
 }  // namespace sandbox
 
 
 #endif  // SANDBOX_SRC_NAMED_PIPE_POLICY_H__