Add chromecast_build gyp variable and add rules when the variable is set to 1.

media/media.gyp

 # Copyright (c) 2012 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.
 
 {
   'variables': {
     'chromium_code': 1,
     # Override to dynamically link the cras (ChromeOS audio) library.
     'use_cras%': 0,
     # Option e.g. for Linux distributions to link pulseaudio directly
     # (DT_NEEDED) instead of using dlopen. This helps with automated
     # detection of ABI mismatches and prevents silent errors.
     'linux_link_pulseaudio%': 0,
     'conditions': [
       ['OS=="android"', {
         # Android doesn't use ffmpeg.
         'media_use_ffmpeg%': 0,
         # Android doesn't use libvpx.
         'media_use_libvpx%': 0,
       }, {  # 'OS!="android"'
         'media_use_ffmpeg%': 1,
         'media_use_libvpx%': 1,
       }],
       # Enable ALSA and Pulse for runtime selection.
-      ['(OS=="linux" or OS=="freebsd" or OS=="solaris") and embedded!=1', {
+      ['(OS=="linux" or OS=="freebsd" or OS=="solaris") and (embedded!=1 or (chromecast==1 and target_arch!="arm"))', {
         # ALSA is always needed for Web MIDI even if the cras is enabled.
         'use_alsa%': 1,
         'conditions': [
           ['use_cras==1', {
             'use_pulseaudio%': 0,
           }, {
             'use_pulseaudio%': 1,
           }],
         ],
       }, {
@@ skipping 1712 matching lines @@
                   ],
                 }],
               ],
             }],
           ],
         },
       ],
     }],
   ],
 }