Move enable extensions define to a build flag.

chrome/utility/extensions/extensions_handler.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 CHROME_UTILITY_EXTENSIONS_EXTENSIONS_HANDLER_H_
 #define CHROME_UTILITY_EXTENSIONS_EXTENSIONS_HANDLER_H_
 
 #include <stdint.h>
 
 #include "base/base64.h"
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "build/build_config.h"
 #include "chrome/common/media_galleries/picasa_types.h"
 #include "chrome/utility/utility_message_handler.h"
+#include "extensions/features/features.h"
 #include "extensions/utility/utility_handler.h"
 
-#if !defined(ENABLE_EXTENSIONS)
+#if !BUILDFLAG(ENABLE_EXTENSIONS)
 #error "Extensions must be enabled"
 #endif
 
 class ChromeContentUtilityClient;
 
 namespace metadata {
 class MediaMetadataParser;
 }
 
 namespace extensions {
@@ skipping 42 matching lines @@
 
   // The client that owns this.
   ChromeContentUtilityClient* const utility_client_;
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionsHandler);
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_UTILITY_EXTENSIONS_EXTENSIONS_HANDLER_H_