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

webrtc/api/video/video_content_type.h

Index: webrtc/api/video/video_content_type.h
diff --git a/webrtc/api/video/video_content_type.h b/webrtc/api/video/video_content_type.h
index 5c468c079d35ea2d20c115234cf38d7e7fcd42bd..6f6bbe8e43971ee3df4ab08e3815f4f1d937b1db 100644
--- a/webrtc/api/video/video_content_type.h
+++ b/webrtc/api/video/video_content_type.h
@@ -18,9 +18,22 @@ namespace webrtc {
 enum class VideoContentType : uint8_t {
   UNSPECIFIED = 0,
   SCREENSHARE = 1,
-  TOTAL_CONTENT_TYPES  // Must be the last value in the enum.
 };
 
+namespace videocontenttypehelpers {
+  bool SetExperimentId(VideoContentType* content_type,
+                              uint8_t experiment_id);
+  bool SetSimulcastId(VideoContentType* content_type,
+                             uint8_t simulcast_id);
+
+  uint8_t GetExperimentId(const VideoContentType& content_type);
+  uint8_t GetSimulcastId(const VideoContentType& content_type);
+
+  bool IsScreenshare(const VideoContentType& content_type);
+
+  bool IsValidContentType(uint8_t value);
+}  // namespace videocontenttypehelpers
+
 }  // namespace webrtc
 
 #endif  // WEBRTC_API_VIDEO_VIDEO_CONTENT_TYPE_H_