Add RTP header extension for HDR metadata

Bug: webrtc:8651
Change-Id: I1c956eaac1532ac0d3820084edb4054a4cc9c68d
Reviewed-on: https://webrtc-review.googlesource.com/c/109924
Commit-Queue: Johannes Kron <kron@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Alex Loiko <aleloi@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25578}

modules/rtp_rtcp/source/rtp_utility.cc

@@ -507,6 +507,10 @@ void RtpHeaderParser::ParseOneByteExtensionHeader(
           RTC_LOG(WARNING)
               << "RtpGenericFrameDescriptor unsupported by rtp header parser.";
           break;
+        case kRtpExtensionHdrMetadata:
+          RTC_LOG(WARNING)
+              << "RtpExtensionHdrMetadata unsupported by rtp header parser.";
+          break;
         case kRtpExtensionNone:
         case kRtpExtensionNumberOfExtensions: {
           RTC_NOTREACHED() << "Invalid extension type: " << type;