Move enable_app_list to a buildflag.

chrome/browser/resources/chromeos/chromevox/strings/BUILD.gn

 # Copyright 2015 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("//chrome/common/features.gni")
 import("//tools/grit/grit_rule.gni")
 
 chromevox_out_dir = "$root_out_dir/resources/chromeos/chromevox"
 
 grit("chromevox_strings") {
   source = "chromevox_strings.grd"
+  defines = chrome_grit_defines
   use_qualified_include = true
   outputs = [
     "_locales/am/messages.json",
     "_locales/ar/messages.json",
     "_locales/bg/messages.json",
     "_locales/bn/messages.json",
     "_locales/ca/messages.json",
     "_locales/cs/messages.json",
     "_locales/da/messages.json",
     "_locales/de/messages.json",
@@ skipping 42 matching lines @@
     "_locales/vi/messages.json",
     "_locales/zh_CN/messages.json",
     "_locales/zh_TW/messages.json",
   ]
   output_dir = chromevox_out_dir
 
   # Don't polute the extension directory with stamp and .d files.
   depfile_dir = target_out_dir
   resource_ids = ""
 }