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

webrtc/modules/rtp_rtcp/source/rtp_utility.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_utility.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_utility.cc b/webrtc/modules/rtp_rtcp/source/rtp_utility.cc
index 4b5ecfa6983d61cba3ebaf9adc74496858c7f4bf..36cac4b53e251286eb0d5e96da05b6590673f28b 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_utility.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_utility.cc
@@ -452,11 +452,9 @@ void RtpHeaderParser::ParseOneByteExtensionHeader(
           //   |  ID   | len=0 | Content type  |
           //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 
-          if (ptr[0] <
-              static_cast<uint8_t>(VideoContentType::TOTAL_CONTENT_TYPES)) {
+          if (VideoContentType::IsValidContentType(ptr[0])) {
             header->extension.hasVideoContentType = true;
-            header->extension.videoContentType =
-                static_cast<VideoContentType>(ptr[0]);
+            header->extension.videoContentType = ptr[0];
           }
           break;
         }