[Chromecast] Set use_alsa=true by default on Chromecast platforms.

media/media.gyp

Index: media/media.gyp
diff --git a/media/media.gyp b/media/media.gyp
index 9e9895be7874a30497e857e0cd3359ac8474ce97..53ea1464421e2d5a1a810bc9be4154af1e549fe5 100644
--- a/media/media.gyp
+++ b/media/media.gyp
@@ -13,11 +13,11 @@
     'linux_link_pulseaudio%': 0,
     'conditions': [
       # Enable ALSA and Pulse for runtime selection.
-      ['(OS=="linux" or OS=="freebsd" or OS=="solaris") and ((embedded!=1 and chromecast==0) or is_cast_desktop_build==1)', {
+      ['(OS=="linux" or OS=="freebsd" or OS=="solaris") and (embedded==0 or chromecast==1)', {

[alokp, 2016/02/10 06:03:13]

I am curious about the difference between gyp and gn. GN does not use embedded
flag?

[slan, 2016/02/10 16:05:23]

I *thought* that |embedded| was not used by builds other than Chromecast, but I
found out that that was an incorrect assumption the last time I touched this
file (https://codereview.chromium.org/1530713006), so I'm being proactive.
|embedded| will not be ported to GN. 

         # ALSA is always needed for Web MIDI even if the cras is enabled.
         'use_alsa%': 1,
         'conditions': [
-          ['use_cras==1', {
+          ['use_cras==1 or chromecast==1', {
             'use_pulseaudio%': 0,
           }, {
             'use_pulseaudio%': 1,