Remove some illegal enum forward declarations

sandbox/win/src/process_mitigations_win32k_policy.h

 // Copyright 2014 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_PROCESS_MITIGATIONS_WIN32K_POLICY_H_
 #define SANDBOX_SRC_PROCESS_MITIGATIONS_WIN32K_POLICY_H_
 
 #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;
-
 // A callback function type to get a function for testing.
 typedef void* (*OverrideForTestFunction)(const char* name);
 
 // This class centralizes most of the knowledge related to the process
 // mitigations Win32K lockdown policy.
 class ProcessMitigationsWin32KLockdownPolicy {
  public:
   // Creates the required low-level policy rules to evaluate a high-level
   // policy rule for the Win32K process mitigation policy.
   // name is the object name, semantics is the desired semantics for the
@@ skipping 58 matching lines @@
 
  private:
   static OverrideForTestFunction override_callback_;
 };
 
 }  // namespace sandbox
 
 #endif  // SANDBOX_SRC_PROCESS_MITIGATIONS_WIN32K_POLICY_H_