Move enable_app_list to a buildflag.

chrome/common/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/buildflag_header.gni")
 import("//build/util/process_version.gni")
 import("//chrome/common/features.gni")
 import("//chrome/process_version_rc_template.gni")  # For branding_file_path.
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//tools/grit/grit_rule.gni")
 
 grit("resources") {
   source = "common_resources.grd"
   use_qualified_include = true
+  defines = chrome_grit_defines
   output_dir = "$root_gen_dir/chrome"
   output_name = "common_resources"
   outputs = [
     "grit/common_resources.h",
     "common_resources.pak",
   ]
 }
 
 buildflag_header("features") {
   header = "features.h"
   flags = [
     "ANDROID_JAVA_UI=$android_java_ui",
+    "ENABLE_APP_LIST=$enable_app_list",
     "ENABLE_BACKGROUND=$enable_background",
     "ENABLE_BASIC_PRINT_DIALOG=$enable_basic_print_dialog",
     "ENABLE_CAPTIVE_PORTAL_DETECTION=$enable_captive_portal_detection",
     "ENABLE_GOOGLE_NOW=$enable_google_now",
     "ENABLE_HANGOUT_SERVICES_EXTENSION=$enable_hangout_services_extension",
     "ENABLE_ONE_CLICK_SIGNIN=$enable_one_click_signin",
     "ENABLE_PACKAGE_MASH_SERVICES=$enable_package_mash_services",
     "ENABLE_PLUGIN_INSTALLATION=$enable_plugin_installation",
     "ENABLE_SERVICE_DISCOVERY=$enable_service_discovery",
     "ENABLE_XPC_NOTIFICATIONS=$enable_xpc_notifications",
@@ skipping 636 matching lines @@
     "shell_handler_win.mojom",
   ]
 
   public_deps = [
     "//skia/public/interfaces",
     "//url/mojo:url_mojom_gurl",
   ]
 
   use_new_wrapper_types = false
 }