[H264][Simulcast] Implement the simulcast logic for h264 encoder

webrtc/modules/rtp_rtcp/source/rtp_format_h264.cc

 /*
  *  Copyright (c) 2014 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 45 matching lines @@
   }
   return true;
 }
 
 bool ParseSingleNalu(RtpDepacketizer::ParsedPayload* parsed_payload,
                      const uint8_t* payload_data,
                      size_t payload_data_length) {
   parsed_payload->type.Video.width = 0;
   parsed_payload->type.Video.height = 0;
   parsed_payload->type.Video.codec = kRtpVideoH264;
+  parsed_payload->type.Video.simulcastIdx = 0;
   parsed_payload->type.Video.isFirstPacket = true;
   RTPVideoHeaderH264* h264_header =
       &parsed_payload->type.Video.codecHeader.H264;
 
   const uint8_t* nalu_start = payload_data + kNalHeaderSize;
   size_t nalu_length = payload_data_length - kNalHeaderSize;
   uint8_t nal_type = payload_data[0] & kTypeMask;
   if (nal_type == kStapA) {
     // Skip the StapA header (StapA nal type + length).
     if (payload_data_length <= kStapAHeaderSize) {
@@ skipping 290 matching lines @@
     // will depacketize the STAP-A into NAL units later.
     if (!ParseSingleNalu(parsed_payload, payload_data, payload_data_length))
       return false;
   }
 
   parsed_payload->payload = payload_data + offset;
   parsed_payload->payload_length = payload_data_length - offset;
   return true;
 }
 }  // namespace webrtc