[Chromecast] Set use_alsa=true only for Chromecast desktop & audio.

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.
 
 import("//build/config/chromecast_build.gni")
 import("//build/config/features.gni")
 import("//testing/libfuzzer/fuzzer_test.gni")
 
 declare_args() {
   # Allows distributions to link pulseaudio directly (DT_NEEDED) instead of
@@ skipping 37 matching lines @@
 
 # Use a second declare_args() to pick up possible overrides of |use_cras|.
 declare_args() {
   # Enables runtime selection of PulseAudio library.
   use_pulseaudio = false
 
   # Enables runtime selection of ALSA library for audio.
   use_alsa = false
 
   # Alsa should be used on non-Android, non-Mac POSIX systems.
-  if (is_posix && !is_android && !is_mac) {
+  # Alsa should be used on desktop Chromecast and audio-only Chromecast builds.
+  if (is_posix && !is_android && !is_mac &&
+      (!is_chromecast || is_cast_desktop_build || disable_display)) {
     use_alsa = true
 
     # Pulse is not supported on Chromecast platforms.
     if (!use_cras && !is_chromecast) {
       use_pulseaudio = true
     }
   }
 }
 
 declare_args() {
@@ skipping 45 matching lines @@
         "cdm",
         "renderer",
       ]
       mojo_media_host = "browser"
     } else {
       mojo_media_services = [ "video_decoder" ]
       mojo_media_host = "gpu"
     }
   }
 }