Add content type information to encoded images and corresponding rtp extension header

webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc b/webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
index d5d4e2f32adbe736dc32d0f68237128df5671bab..acbe3eec6434808ab4f4cf2d62696d4fc25bc248 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
@@ -41,6 +41,8 @@ RTPExtensionType StringToRtpExtensionType(const std::string& extension) {
     return kRtpExtensionTransportSequenceNumber;
   if (extension == RtpExtension::kPlayoutDelayUri)
     return kRtpExtensionPlayoutDelay;
+  if (extension == RtpExtension::kVideoContentTypeUri)
+    return kRtpExtensionVideoContentType;
   RTC_NOTREACHED() << "Looking up unsupported RTP extension.";
   return kRtpExtensionNone;
 }