Move enable extensions define to a build flag.

chrome/common/extensions/chrome_utility_extensions_messages.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.
 
 // Multiply-included message file, so no include guard.
 
 #include <stdint.h>
 
 #include <string>
 #include <vector>
 
 #include "base/files/file_path.h"
 #include "build/build_config.h"
 #include "chrome/common/media_galleries/itunes_library.h"
 #include "chrome/common/media_galleries/metadata_types.h"
 #include "chrome/common/media_galleries/picasa_types.h"
+#include "extensions/features/features.h"
 #include "ipc/ipc_message_macros.h"
 #include "ipc/ipc_platform_file.h"
 
-#if !defined(ENABLE_EXTENSIONS)
+#if !BUILDFLAG(ENABLE_EXTENSIONS)
 #error "Extensions must be enabled"
 #endif
 
 #define IPC_MESSAGE_START ChromeUtilityExtensionsMsgStart
 
 #if defined(OS_WIN) || defined(OS_MACOSX)
 IPC_STRUCT_TRAITS_BEGIN(itunes::parser::Track)
   IPC_STRUCT_TRAITS_MEMBER(id)
   IPC_STRUCT_TRAITS_MEMBER(location)
 IPC_STRUCT_TRAITS_END()
@@ skipping 158 matching lines @@
 // elevation).
 IPC_MESSAGE_CONTROL1(ChromeUtilityHostMsg_GetWiFiCredentials,
                      std::string /* ssid */)
 
 // Reply after getting WiFi credentials from the system. |success| is false if
 // error occurred.
 IPC_MESSAGE_CONTROL2(ChromeUtilityHostMsg_GotWiFiCredentials,
                      std::string /* key_data */,
                      bool /* success */)
 #endif  // defined(OS_WIN)