Rename is_chromeos in chrome/src.

chrome/browser/resources/chromeos/chromevox/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("//build/config/features.gni")
 import("//testing/test.gni")
 import("//chrome/test/base/js2gtest.gni")
 import("chromevox.gni")
 
-assert(is_chromeos)
+assert(use_cros_fe)
 
 declare_args() {
   # Whether to compress the main Chromevox javascript files or load the
   # modules individually from source files.
   chromevox_compress_js = !is_debug
 }
 
 chromevox_out_dir = "$root_out_dir/resources/chromeos/chromevox"
 
 group("chromevox") {
@@ skipping 363 matching lines @@
   ]
   defines = [ "HAS_OUT_OF_PROC_TEST_RUNNER" ]
 }
 
 js2gtest("chromevox_extjs_tests") {
   test_type = "extension"
   sources = chromevox_tests_gypi_values.chromevox_tests_extjs_sources
   sources -= [ "braille/liblouis_test.extjs" ]  # TODO(GYP)
   defines = [ "HAS_OUT_OF_PROC_TEST_RUNNER" ]
 }