In Vp9 encoder wrapper force key frame on svc controller request

Bug: chromium:1349761
Change-Id: I865a251ea87b0946ff0247cba5c3bf1e098dffab
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/270482
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Commit-Queue: Danil Chapovalov <danilchap@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#37684}

modules/video_coding/codecs/vp9/libvpx_vp9_encoder.cc

@@ -1004,6 +1004,9 @@ int LibvpxVp9Encoder::Encode(const VideoFrame& input_image,
     if (layer_frames_.empty()) {
       return WEBRTC_VIDEO_CODEC_ERROR;
     }
+    if (layer_frames_.front().IsKeyframe()) {
+      force_key_frame_ = true;
+    }
   }
 
   vpx_svc_layer_id_t layer_id = {0};