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

webrtc/modules/rtp_rtcp/source/rtp_utility.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 439 matching lines @@
           if (len != 0) {
             LOG(LS_WARNING) << "Incorrect video content type len: " << len;
             return;
           }
           //    0                   1
           //    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
           //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
           //   |  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;
         }
         case kRtpExtensionVideoTiming: {
           if (len != VideoTimingExtension::kValueSizeBytes - 1) {
             LOG(LS_WARNING) << "Incorrect video timing len: " << len;
             return;
           }
           header->extension.has_video_timing = true;
           VideoTimingExtension::Parse(rtc::MakeArrayView(ptr, len + 1),
@@ skipping 15 matching lines @@
           return;
         }
       }
     }
     ptr += (len + 1);
   }
 }
 
 }  // namespace RtpUtility
 }  // namespace webrtc