(factory-980B) factory_Audio: allow initializing volume.

Partners may perfer larger volume when testing audio.

BUG=none, found by partner suggestion
TEST=add audio_init_volume=90 in test_list and finished audio test.

Change-Id: Ic9be7d7d43d15b1da5ba1fa80d0f8d610f207c20
Reviewed-on: http://gerrit.chromium.org/gerrit/10394
Commit-Ready: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: Hung-Te Lin <hungte@chromium.org>
diff --git a/client/site_tests/factory_Audio/factory_Audio.py b/client/site_tests/factory_Audio/factory_Audio.py
index 8c81415..ac8031f 100644
--- a/client/site_tests/factory_Audio/factory_Audio.py
+++ b/client/site_tests/factory_Audio/factory_Audio.py
@@ -185,10 +185,14 @@
             raise error.TestFail('ERROR: Unable to find audio sample %s' % path)
         return path
 
-    def run_once(self, audio_sample_path=None):
+    def run_once(self, audio_sample_path=None, audio_init_volume=None):
 
         factory.log('%s run_once' % self.__class__)
 
+        # Change initial volume.
+        if audio_sample_path:
+            os.system("amixer -c 0 sset Master %d%%" % audio_init_volume)
+
         # Write recordings in tmpdir.
         os.chdir(self.tmpdir)