OnReceivedUplinkPacketLossFraction() receives [const rtc::Optional<float>&]

webrtc/modules/audio_coding/codecs/audio_encoder.h

Index: webrtc/modules/audio_coding/codecs/audio_encoder.h
diff --git a/webrtc/modules/audio_coding/codecs/audio_encoder.h b/webrtc/modules/audio_coding/codecs/audio_encoder.h
index 47152f9eee1ae4f9532186b1ca69f56bcdf36b8f..00b7f4619e74f845c0f695104c7bcb1a5ed5c4c5 100644
--- a/webrtc/modules/audio_coding/codecs/audio_encoder.h
+++ b/webrtc/modules/audio_coding/codecs/audio_encoder.h
@@ -171,9 +171,9 @@ class AudioEncoder {
   virtual void DisableAudioNetworkAdaptor();
 
   // Provides uplink packet loss fraction to this encoder to allow it to adapt.
-  // |uplink_packet_loss_fraction| is in the range [0.0, 1.0].
+  // |uplink_packet_loss_fraction| is in the range [0.0, 1.0] or unknown.
   virtual void OnReceivedUplinkPacketLossFraction(
-      float uplink_packet_loss_fraction);
+      const rtc::Optional<float>& uplink_packet_loss_fraction);
 
   // Provides target audio bitrate to this encoder to allow it to adapt.
   virtual void OnReceivedTargetAudioBitrate(int target_bps);