message: Fix/device id firefox
diff: @@ -141,10 +141,19 @@ Erizo.GetUserMedia = function (config, callback, error) {
  } else {
  if (config.video && Erizo.getBrowser() === 'mozilla') {
  var ffConfig = {video:{}, audio: config.audio, screen: config.screen};
  + if (config.audio.mandatory !== undefined) {
  + var audioCfg = config.audio.mandatory;
  + if (audioCfg.sourceId) {
  + ffConfig.audio.deviceId = audioCfg.sourceId;
  + }
  + }
  if (config.video.mandatory !== undefined) {
  var videoCfg = config.video.mandatory;
  ffConfig.video.width = {min: videoCfg.minWidth, max: videoCfg.maxWidth};
  ffConfig.video.height = {min: videoCfg.minHeight, max: videoCfg.maxHeight};
  + if (videoCfg.sourceId) {
  + ffConfig.video.deviceId = videoCfg.sourceId;
  + }
  }
  if (config.video.optional !== undefined) {
  