Remove NOTIFICATION_EXTENSION_ENABLED.

extensions/browser/BUILD.gn

 # 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/features.gni")
 import("//extensions/features/features.gni")
 
 assert(enable_extensions)
 
 group("browser") {
@@ skipping 66 matching lines @@
     "deferred_start_render_host_observer.h",
     "error_map.cc",
     "error_map.h",
     "event_listener_map.cc",
     "event_listener_map.h",
     "event_page_tracker.h",
     "event_router.cc",
     "event_router.h",
     "event_router_factory.cc",
     "event_router_factory.h",
+    "events/lazy_event_dispatch_util.cc",
+    "events/lazy_event_dispatch_util.h",
     "extension_api_frame_id_map.cc",
     "extension_api_frame_id_map.h",
     "extension_dialog_auto_confirm.cc",
     "extension_dialog_auto_confirm.h",
     "extension_error.cc",
     "extension_error.h",
     "extension_function.cc",
     "extension_function.h",
     "extension_function_dispatcher.cc",
     "extension_function_dispatcher.h",
@@ skipping 417 matching lines @@
       "api/media_perception_private/media_perception_api_manager_unittest.cc",
       "api/webcam_private/visca_webcam_unittest.cc",
     ]
 
     deps += [
       "//chromeos:media_perception_proto",
       "//chromeos:test_support",
     ]
   }
 }