Add periodic logging of video stats.

webrtc/call/call.cc

Index: webrtc/call/call.cc
diff --git a/webrtc/call/call.cc b/webrtc/call/call.cc
index 51e0cceac98d84b8eb87774232b54075087d5228..af88d09ca6e2a2c739d1da8294a64f0faac15f67 100644
--- a/webrtc/call/call.cc
+++ b/webrtc/call/call.cc
@@ -201,6 +201,18 @@ class Call : public webrtc::Call,
 };
 }  // namespace internal
 
+std::string Call::Stats::ToString(int64_t time_ms) const {
+  std::stringstream ss;
+  ss << "Call stats:" << time_ms << ", {";
+  ss << "send_bw_bps:" << send_bandwidth_bps << ", ";
+  ss << "recv_bw_bps:" << recv_bandwidth_bps << ", ";
+  ss << "max_pad_bps:" << max_padding_bitrate_bps << ", ";
+  ss << "pacer_delay_ms:" << pacer_delay_ms << ", ";
+  ss << "rtt_ms:" << rtt_ms;
+  ss << '}';
+  return ss.str();
+}
+
 Call* Call::Create(const Call::Config& config) {
   return new internal::Call(config);
 }