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

webrtc/modules/video_coding/include/video_codec_interface.h

Index: webrtc/modules/video_coding/include/video_codec_interface.h
diff --git a/webrtc/modules/video_coding/include/video_codec_interface.h b/webrtc/modules/video_coding/include/video_codec_interface.h
index 19303c0d6783ed47cdd07a7f7461ca059bc59e69..5428352889e14ae07caa68d8d319ca230e68ce6f 100644
--- a/webrtc/modules/video_coding/include/video_codec_interface.h
+++ b/webrtc/modules/video_coding/include/video_codec_interface.h
@@ -77,7 +77,9 @@ struct CodecSpecificInfoGeneric {
   uint8_t simulcast_idx;
 };
 
-struct CodecSpecificInfoH264 {};
+struct CodecSpecificInfoH264 {
+  uint8_t simulcastIdx;
+};
 
 union CodecSpecificInfoUnion {
   CodecSpecificInfoGeneric generic;