H.264 temporal layers w/frame marking (PART 2/3)

Bug: None
Change-Id: Id1381d895377d39c3969635e1a59591214aabb71
Reviewed-on: https://webrtc-review.googlesource.com/c/86140
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Sergey Silkin <ssilkin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26624}

api/video_codecs/video_codec.h

@@ -82,6 +82,7 @@ struct VideoCodecH264 {
   }
   bool frameDroppingOn;
   int keyFrameInterval;
+  uint8_t numberOfTemporalLayers;
   // These are NULL/0 if not externally negotiated.
   const uint8_t* spsData;
   size_t spsLen;