Implement FrameMarking header extension support

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 82 matching lines @@
       case kRtpExtensionRtpStreamId: {
         std::string rsid;
         packet.GetExtension<RtpStreamId>(&rsid);
         break;
       }
       case kRtpExtensionRepairedRtpStreamId: {
         std::string rsid;
         packet.GetExtension<RepairedRtpStreamId>(&rsid);
         break;
       }
+      case kRtpExtensionFrameMarking: {
+        FrameMarks frame_marks;
+        packet.GetExtension<FrameMarking>(&frame_marks);
+        break;
+      }
     }
   }
 }
 }  // namespace webrtc