Move enable extensions define to a build flag.

chrome/browser/extensions/extension_service.h

 // Copyright (c) 2012 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_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_
 
 #include <map>
 #include <memory>
 #include <set>
@@ skipping 16 matching lines @@
 #include "content/public/browser/notification_registrar.h"
 #include "extensions/browser/crx_file_info.h"
 #include "extensions/browser/extension_prefs.h"
 #include "extensions/browser/external_provider_interface.h"
 #include "extensions/browser/install_flag.h"
 #include "extensions/browser/process_manager.h"
 #include "extensions/browser/uninstall_reason.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/extension_set.h"
 #include "extensions/common/manifest.h"
+#include "extensions/features/features.h"
 
-#if !defined(ENABLE_EXTENSIONS)
+#if !BUILDFLAG(ENABLE_EXTENSIONS)
 #error "Extensions must be enabled"
 #endif
 
 class GURL;
 class HostContentSettingsMap;
 class Profile;
 
 namespace base {
 class CommandLine;
 class SequencedTaskRunner;
@@ skipping 707 matching lines @@
                            GreylistUnknownDontChange);
   FRIEND_TEST_ALL_PREFIXES(ExtensionServiceTest,
                            ManagementPolicyProhibitsEnableOnInstalled);
   FRIEND_TEST_ALL_PREFIXES(ExtensionServiceTest,
                            BlockAndUnblockBlacklistedExtension);
 
   DISALLOW_COPY_AND_ASSIGN(ExtensionService);
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_SERVICE_H_