Enable H.264 temporal scalability in simulcast.

Bug: webrtc:10651
Change-Id: I58372186930ce33e925f85edb0f308657dbfe273
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/142840
Reviewed-by: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Commit-Queue: Sergey Silkin <ssilkin@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28381}
diff --git a/media/engine/simulcast_encoder_adapter.cc b/media/engine/simulcast_encoder_adapter.cc
index 6d8bedb..596c975 100644
--- a/media/engine/simulcast_encoder_adapter.cc
+++ b/media/engine/simulcast_encoder_adapter.cc
@@ -585,6 +585,9 @@
       // Turn off denoising for all streams but the highest resolution.
       stream_codec->VP8()->denoisingOn = false;
     }
+  } else if (inst.codecType == webrtc::kVideoCodecH264) {
+    stream_codec->H264()->numberOfTemporalLayers =
+        inst.simulcastStream[stream_index].numberOfTemporalLayers;
   }
   // TODO(ronghuawu): what to do with targetBitrate.