Reland of 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 543688c75e8c91ec36006ce8026b7c6e8e0ca7a9..0d30848f965cd09776e13163eb44e11c85db817e 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h
+++ b/webrtc/modules/rtp_rtcp/source/rtp_header_extensions.h
@@ -12,6 +12,7 @@
 
 #include <stdint.h>
 
+#include "webrtc/api/video/video_content_type.h"
 #include "webrtc/api/video/video_rotation.h"
 #include "webrtc/base/array_view.h"
 #include "webrtc/modules/rtp_rtcp/include/rtp_rtcp_defines.h"
@@ -98,5 +99,17 @@ class PlayoutDelayLimits {
   static bool Write(uint8_t* data, const PlayoutDelay& playout_delay);
 };
 
+class VideoContentTypeExtension {
+ public:
+  static constexpr RTPExtensionType kId = kRtpExtensionVideoContentType;
+  static constexpr uint8_t kValueSizeBytes = 1;
+  static constexpr const char* kUri =
+      "http://www.webrtc.org/experiments/rtp-hdrext/video-content-type";
+
+  static bool Parse(rtc::ArrayView<const uint8_t> data,
+                    VideoContentType* content_type);
+  static bool Write(uint8_t* data, VideoContentType content_type);
+};
+
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_RTP_HEADER_EXTENSIONS_H_