Propagate scalability mode in CreateSimulcastOrConferenceModeScreenshareStreams.

Bug: webrtc:11607
Change-Id: I0b14ea38026bccdb8f4bf1217fe2f9fa41f1c90e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/234344
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#35178}

media/engine/webrtc_video_engine.cc

diff --git a/media/engine/webrtc_video_engine.cc b/media/engine/webrtc_video_engine.cc
index c11f29b..cc6e29a 100644
--- a/media/engine/webrtc_video_engine.cc
+++ b/media/engine/webrtc_video_engine.cc
@@ -3692,6 +3692,8 @@
 
   for (size_t i = 0; i < layers.size(); ++i) {
     layers[i].active = encoder_config.simulcast_layers[i].active;
+    layers[i].scalability_mode =
+        encoder_config.simulcast_layers[i].scalability_mode;
     // Update with configured num temporal layers if supported by codec.
     if (encoder_config.simulcast_layers[i].num_temporal_layers &&
         IsTemporalLayersSupported(codec_name_)) {