Implement get ringer mode.

lib/roles/device/plugins/service.js

@@ -552,6 +552,25 @@ module.exports = syrup.serial()
         })
     }
 
+    plugin.getRingerMode = function() {
+      return runServiceCommand(
+          apk.wire.MessageType.GET_RINGER_MODE
+        , new apk.wire.GetRingerModeRequest()
+        )
+        .timeout(10000)
+        .then(function(data) {
+          var response = apk.wire.GetRingerModeResponse.decode(data)
+          // Reflection to decode enums to their string values, otherwise
+          // we only get an integer
+          var ringerMode = apk.builder.lookup('jp.co.cyberagent.stf.proto.RingerMode')
+            .children[response.mode].name
+          if (response.success) {
+            return ringerMode
+          }
+          throw new Error('Unable to get ringer mode')
+        })
+    }
+
     plugin.setWifiEnabled = function(enabled) {
       return runServiceCommand(
           apk.wire.MessageType.SET_WIFI_ENABLED