Adds AppListDelegate to AppList that is notified on visibility changes

ui/app_list/presenter/BUILD.gn

 # Copyright 2016 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/ui.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 
 assert(use_aura)
 
 mojom("mojom") {
   sources = [
     "app_list_presenter.mojom",
   ]
   deps = [
     "//services/ui/public/interfaces",
   ]
 
   export_class_attribute = "APP_LIST_PRESENTER_EXPORT"
   export_define = "APP_LIST_PRESENTER_IMPLEMENTATION=1"
   export_header = "ui/app_list/presenter/app_list_presenter_export.h"
 }
 
 component("presenter") {
   sources = [
     "app_list.cc",
     "app_list.h",
+    "app_list_delegate.h",
     "app_list_presenter_delegate.cc",
     "app_list_presenter_delegate.h",
     "app_list_presenter_delegate_factory.h",
     "app_list_presenter_export.h",
     "app_list_presenter_impl.cc",
     "app_list_presenter_impl.h",
     "app_list_view_delegate_factory.cc",
     "app_list_view_delegate_factory.h",
   ]
 
@@ skipping 63 matching lines @@
 
     # Temporary dependency to fix compile flake in http://crbug.com/611898.
     # TODO(tapted): Remove once http://crbug.com/612382 is fixed.
     "//ui/accessibility:ax_gen",
   ]
 
   data_deps = [
     "//ui/resources:ui_test_pak_data",
   ]
 }