Piggybacking simulcast id and ALR experiment id into video content type extension.

webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc b/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
index 28685b4640a9e123c55ecb5a2003dd018ddf9c89..d409d5a6199f9466c5982595da15bc167987bc9f 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.cc
@@ -232,7 +232,7 @@ constexpr const char VideoContentTypeExtension::kUri[];
 bool VideoContentTypeExtension::Parse(rtc::ArrayView<const uint8_t> data,
                                       VideoContentType* content_type) {
   if (data.size() == 1 &&
-      data[0] < static_cast<uint8_t>(VideoContentType::TOTAL_CONTENT_TYPES)) {
+      videocontenttypehelpers::IsValidContentType(data[0])) {
     *content_type = static_cast<VideoContentType>(data[0]);
     return true;
   }