Implement PlayoutDelay extension as a trait

webrtc/test/fuzzers/rtp_packet_fuzzer.cc

 /*
  *  Copyright (c) 2016 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 64 matching lines @@
         break;
       case kRtpExtensionVideoRotation:
         uint8_t rotation;
         packet.GetExtension<VideoOrientation>(&rotation);
         break;
       case kRtpExtensionTransportSequenceNumber:
         uint16_t seqnum;
         packet.GetExtension<TransportSequenceNumber>(&seqnum);
         break;
       case kRtpExtensionPlayoutDelay:
-        // TODO(katrielc) Add this once it's written.
+        PlayoutDelay playout;
+        packet.GetExtension<PlayoutDelayLimits>(&playout);
         break;
     }
   }
 }
 }  // namespace webrtc