Temporary add 'RTPVideoHeaderH264::nalus_length'.

This is a forward fix for https://webrtc-review.googlesource.com/c/src/+/354622 that breaks client code using nalus_length.

No-Try: true
Change-Id: Ic0fc41696e408adefe4eb8792150a64b1eab49da
Bug: None
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/354840
Reviewed-by: Danil Chapovalov <danilchap@webrtc.org>
Commit-Queue: Jeremy Leconte <jleconte@google.com>
Owners-Override: Jeremy Leconte <jleconte@google.com>
Cr-Commit-Position: refs/heads/main@{#42493}
diff --git a/modules/rtp_rtcp/source/video_rtp_depacketizer_h264.cc b/modules/rtp_rtcp/source/video_rtp_depacketizer_h264.cc
index e6b206cd..07a9e74 100644
--- a/modules/rtp_rtcp/source/video_rtp_depacketizer_h264.cc
+++ b/modules/rtp_rtcp/source/video_rtp_depacketizer_h264.cc
@@ -221,6 +221,7 @@
     }
 
     h264_header.nalus.push_back(nalu);
+    ++h264_header.nalus_length;
   }
 
   return parsed_payload;
@@ -279,6 +280,7 @@
   h264_header.nalu_type = original_nal_type;
   if (first_fragment) {
     h264_header.nalus = {nalu};
+    h264_header.nalus_length = 1;
   }
   return parsed_payload;
 }
diff --git a/modules/video_coding/codecs/h264/include/h264_globals.h b/modules/video_coding/codecs/h264/include/h264_globals.h
index dac36dd..64a3829 100644
--- a/modules/video_coding/codecs/h264/include/h264_globals.h
+++ b/modules/video_coding/codecs/h264/include/h264_globals.h
@@ -83,6 +83,8 @@
   // The packetization type of this buffer - single, aggregated or fragmented.
   H264PacketizationTypes packetization_type;
   std::vector<NaluInfo> nalus;
+  // TODO - jleconte: Remove 'nalus_length' once all the code has been migrated.
+  size_t nalus_length;
   // The packetization mode of this transport. Packetization mode
   // determines which packetization types are allowed when packetizing.
   H264PacketizationMode packetization_mode;