In VideoEngine also respect requested TL number even for screenshare

Bug: chromium:927208
Change-Id: Ic20b2da246dac9185375cc42a6a2505aaff95ac6
Reviewed-on: https://webrtc-review.googlesource.com/c/121403
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26546}
diff --git a/api/rtp_parameters.h b/api/rtp_parameters.h
index a2c566a..25a21c1 100644
--- a/api/rtp_parameters.h
+++ b/api/rtp_parameters.h
@@ -461,7 +461,7 @@
   // supported by the codec implementation).
   // TODO(asapersson): Different number of temporal layers are not supported
   // per simulcast layer.
-  // Not supported for screencast.
+  // Screencast support is experimental.
   absl::optional<int> num_temporal_layers;
 
   // For video, scale the resolution down by this factor.