Move enable extensions define to a build flag.

chrome/chrome_repack_locales.gni

 # 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.
 
 import("//build/config/chrome_build.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
+import("//extensions/features/features.gni")
 import("//tools/grit/repack.gni")
 
 # Wraps repack_locales(), setting the source_patterns and deps required for
 # Chrome.
 #
 # Extra Parameters:
 #
 #   additional_source_patterns [optional]
 #      Extra source_patterns for repack_locales().
 template("chrome_repack_locales") {
@@ skipping 86 matching lines @@
         "//chrome/app:chromium_strings",
         "//components/strings:components_chromium_strings",
       ]
     }
 
     if (defined(invoker.additional_source_patterns)) {
       source_patterns += invoker.additional_source_patterns
     }
   }
 }