Enable audio streams to send padding.

webrtc/modules/pacing/packet_router.cc

Index: webrtc/modules/pacing/packet_router.cc
diff --git a/webrtc/modules/pacing/packet_router.cc b/webrtc/modules/pacing/packet_router.cc
index 65d6db7cb704015cb6dac0fa2e6f309fe93f8440..3deb3a8faf1e757630e4fc29f856343074d18f02 100644
--- a/webrtc/modules/pacing/packet_router.cc
+++ b/webrtc/modules/pacing/packet_router.cc
@@ -72,7 +72,7 @@ size_t PacketRouter::TimeToSendPadding(size_t bytes_to_send,
   rtc::CritScope cs(&modules_crit_);
   // Rtp modules are ordered by which stream can most benefit from padding.
   for (RtpRtcp* module : rtp_modules_) {
-    if (module->SendingMedia()) {
+    if (module->SendingMedia() && module->HasBweExtensions()) {
       size_t bytes_sent = module->TimeToSendPadding(
           bytes_to_send - total_bytes_sent, probe_cluster_id);
       total_bytes_sent += bytes_sent;