Rename is_chromeos in chrome/src.

media/media_options.gni

 # 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.
 
 declare_args() {
   # Allows distributions to link pulseaudio directly (DT_NEEDED) instead of
   # using dlopen. This helps with automated detection of ABI mismatches and
   # prevents silent errors.
   link_pulseaudio = false
 
@@ skipping 20 matching lines @@
   use_cras = false
 
   # Enables runtime selection of PulseAudio library.
   use_pulseaudio = false
 
   # Enables runtime selection of ALSA library for audio.
   use_alsa = false
 
   # TODO(GYP): How to handled the "embedded" use case?
   # Original conditional: (OS=="linux" or OS=="freebsd" or OS=="solaris") and embedded!=1
-  if (is_posix && !is_android && !is_mac) {
+  if (is_posix && !is_android && !is_mac && !is_chromeos_os) {
     use_alsa = true
     if (!use_cras) {
       use_pulseaudio = true
     }
   }
 
   # Enables the MPEG2-TS stream parser for use with Media Source. Disabled by
   # default since it's not available on the normal Web Platform and costs money.
   enable_mpeg2ts_stream_parser = false
 
   # Experiment to enable mojo media application: http://crbug.com/431776
   # Valid options are:
   # - "none": Do not use mojo media application.
   # - "browser": Use mojo media application hosted in the browser process.
   # - "utility": Use mojo media application hosted in the utility process.
   enable_mojo_media = "none"
 
   # TODO(GYP): This should be a platform define.
   is_openbsd = false
 }