Add functionality to set min bitrate for single stream through RtpEncodingParameters.

Bug: webrtc:9341
Change-Id: Ia1e819bd61dbef9c93d0ba84907faeeebf925db2
Reviewed-on: https://webrtc-review.googlesource.com/80261
Commit-Queue: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Taylor Brandstetter <deadbeef@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23722}
diff --git a/api/video_codecs/video_encoder_config.h b/api/video_codecs/video_encoder_config.h
index 47ff925..e10f081 100644
--- a/api/video_codecs/video_encoder_config.h
+++ b/api/video_codecs/video_encoder_config.h
@@ -146,6 +146,8 @@
   // The simulcast layer's configurations set by the application for this video
   // sender. These are modified by the video_stream_factory before being passed
   // down to lower layers for the video encoding.
+  // |simulcast_layers| is also used for configuring non-simulcast (when there
+  // is a single VideoStream).
   std::vector<VideoStream> simulcast_layers;
 
   // Max number of encoded VideoStreams to produce.