message: sdp: use exact match in parseMediaDescription
  Cr-Commit-Position: refs/heads/master@{#31571}
diff: @@ -2656,17 +2656,18 @@ bool ParseMediaDescription(
  std::string content_name;
  bool bundle_only = false;
  int section_msid_signaling = 0;
  - if (HasAttribute(line, kMediaTypeVideo)) {
  + std::string mediaType = fields[0];
  + if (mediaType == kMediaTypeVideo) {
  content = ParseContentDescription<VideoContentDescription>(
  message, cricket::MEDIA_TYPE_VIDEO, mline_index, protocol,
  payload_types, pos, &content_name, &bundle_only,
  &section_msid_signaling, &transport, candidates, error);
  - } else if (HasAttribute(line, kMediaTypeAudio)) {
  + } else if (mediaType == kMediaTypeAudio) {
  content = ParseContentDescription<AudioContentDescription>(
  message, cricket::MEDIA_TYPE_AUDIO, mline_index, protocol,
  payload_types, pos, &content_name, &bundle_only,
  &section_msid_signaling, &transport, candidates, error);
  - } else if (HasAttribute(line, kMediaTypeData)) {
  + } else if (mediaType == kMediaTypeData) {
  if (cricket::IsDtlsSctp(protocol)) {
  // The draft-03 format is:
  // m=application <port> DTLS/SCTP <sctp-port>...
  