message: sdp: ignore legacy sctpmap line
  and reorganise the parsing
  Cr-Commit-Position: refs/heads/master@{#32843}
diff: @@ -3128,8 +3128,11 @@ bool ParseContent(const std::string& message,
  if (!ParseDtlsSetup(line, &(transport->connection_role), error)) {
  return false;
  }
  - } else if (cricket::IsDtlsSctp(protocol) &&
  - HasAttribute(line, kAttributeSctpPort)) {
  + } else if (cricket::IsDtlsSctp(protocol)) {
  + //
  + // SCTP specific attributes
  + //
  + if (HasAttribute(line, kAttributeSctpPort)) {
  if (media_type != cricket::MEDIA_TYPE_DATA) {
  return ParseFailed(
  line, "sctp-port attribute found in non-data media description.",
  @@ -3144,8 +3147,7 @@ bool ParseContent(const std::string& message,
  return false;
  }
  media_desc->as_sctp()->set_port(sctp_port);
  - } else if (cricket::IsDtlsSctp(protocol) &&
  - HasAttribute(line, kAttributeMaxMessageSize)) {
  + } else if (HasAttribute(line, kAttributeMaxMessageSize)) {
  if (media_type != cricket::MEDIA_TYPE_DATA) {
  return ParseFailed(
  line,
  @@ -3157,9 +3159,13 @@ bool ParseContent(const std::string& message,
  return false;
  }
  media_desc->as_sctp()->set_max_message_size(max_message_size);
  + } else if (HasAttribute(line, kAttributeSctpmap)) {
  + // Ignore a=sctpmap: from early versions of draft-ietf-mmusic-sctp-sdp
  + continue;
  + }
  } else if (cricket::IsRtpProtocol(protocol)) {
  //
  - // RTP specific attrubtes
  + // RTP specific attributes
  //
  if (HasAttribute(line, kAttributeRtcpMux)) {
  media_desc->set_rtcp_mux(true);
  