Move enable_app_list to a buildflag.

chrome/browser/ui/app_list/app_list_util.cc

 // Copyright 2013 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.
 
 #include "chrome/browser/ui/app_list/app_list_util.h"
 
 #include "build/build_config.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/common/pref_names.h"
 #include "components/prefs/pref_service.h"
 
 bool IsAppLauncherEnabled() {
-#if !defined(ENABLE_APP_LIST)
+#if !BUILDFLAG(ENABLE_APP_LIST)
   return false;
 #elif defined(OS_CHROMEOS) || defined(USE_ASH)
   return true;
 #else
   PrefService* prefs = g_browser_process->local_state();
   // In some tests, the prefs aren't initialised.
   return prefs && prefs->GetBoolean(prefs::kAppLauncherHasBeenEnabled);
 #endif
 }
 
 bool ShouldShowAppLauncherPromo() {
   // Never promote. TODO(tapted): Delete this function and supporting code.
   return false;
 }