Add ToString method to AggregatedStats and log stats at the end of a call.

webrtc/video/receive_statistics_proxy.cc

Index: webrtc/video/receive_statistics_proxy.cc
diff --git a/webrtc/video/receive_statistics_proxy.cc b/webrtc/video/receive_statistics_proxy.cc
index ded510a55e77dafee3fa9f217c3311d2224daf32..b15ef682a1d587d46634e0a74ceb73fe9a533b67 100644
--- a/webrtc/video/receive_statistics_proxy.cc
+++ b/webrtc/video/receive_statistics_proxy.cc
@@ -77,6 +77,8 @@ void ReceiveStatisticsProxy::UpdateHistograms() {
   if (freq_offset_stats.num_samples > 0) {
     RTC_HISTOGRAM_COUNTS_10000("WebRTC.Video.RtpToNtpFreqOffsetInKhz",
                                freq_offset_stats.average);
+    LOG(LS_INFO) << "WebRTC.Video.RtpToNtpFreqOffsetInKhz, "
+                 << freq_offset_stats.ToString();
   }
 
   int qp = qp_counters_.vp8.Avg(kMinRequiredSamples);