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

webrtc/modules/video_coding/include/video_codec_interface.h

 /*
  *  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 59 matching lines @@
 
   // Frame reference data.
   uint8_t num_ref_pics;
   uint8_t p_diff[kMaxVp9RefPics];
 };
 
 struct CodecSpecificInfoGeneric {
   uint8_t simulcast_idx;
 };
 
-struct CodecSpecificInfoH264 {};
+struct CodecSpecificInfoH264 {
+  uint8_t simulcastIdx;
+};
 
 union CodecSpecificInfoUnion {
   CodecSpecificInfoGeneric generic;
   CodecSpecificInfoVP8 VP8;
   CodecSpecificInfoVP9 VP9;
   CodecSpecificInfoH264 H264;
 };
 
 // Note: if any pointers are added to this struct or its sub-structs, it
 // must be fitted with a copy-constructor. This is because it is copied
 // in the copy-constructor of VCMEncodedFrame.
 struct CodecSpecificInfo {
   VideoCodecType codecType;
   CodecSpecificInfoUnion codecSpecific;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_VIDEO_CODING_INCLUDE_VIDEO_CODEC_INTERFACE_H_