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")
 
 group("browser") {
   public_deps = [
     "//extensions/browser:browser_context_keyed_service_factories",
@@ skipping 102 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 377 matching lines @@
 
   if (is_chromeos) {
     sources += [
       "api/audio/audio_device_id_calculator_unittest.cc",
       "api/webcam_private/visca_webcam_unittest.cc",
     ]
 
     deps += [ "//chromeos:test_support" ]
   }
 }