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

webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h

Index: webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h b/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h
index ea6f9dbc9c140c24504ca3aaf98f40071e601216..bf9eb70abb671ef9a48212ca3ca90a65eeca578f 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h
+++ b/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h
@@ -13,6 +13,7 @@
 #include <stdint.h>
 
 #include "webrtc/api/video/video_rotation.h"
+#include "webrtc/api/video/video_content_type.h"
 #include "webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h"
 
 namespace webrtc {
@@ -96,5 +97,16 @@ class PlayoutDelayLimits {
   static bool Write(uint8_t* data, const PlayoutDelay& playout_delay);
 };
 
+class VideoContentType {
+ public:
+  static constexpr RTPExtensionType kId = kRtpExtensionVideoContentType;
+  static constexpr uint8_t kValueSizeBytes = 1;
+  // TODO(ilnik): Think of a better URI.
+  static constexpr const char* kUri = "urn:webrtc:video-content-type";
+
+  static bool Parse(const uint8_t* data, VideoContentTypeId* content_type);
+  static bool Write(uint8_t* data, VideoContentTypeId content_type);
+};
+
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_RTP_HEADER_EXTENSIONS_H_