Trace stats in RTCStatsCollector.

webrtc/pc/rtcstatscollector.cc

Index: webrtc/pc/rtcstatscollector.cc
diff --git a/webrtc/pc/rtcstatscollector.cc b/webrtc/pc/rtcstatscollector.cc
index f5b8c8a936c1b569826ff20d98741e62ddb5e550..0fee0b0497546edf032d51c6e7ed3bd79f45bed8 100644
--- a/webrtc/pc/rtcstatscollector.cc
+++ b/webrtc/pc/rtcstatscollector.cc
@@ -25,11 +25,19 @@
 #include "webrtc/pc/webrtcsession.h"
 #include "webrtc/rtc_base/checks.h"
 #include "webrtc/rtc_base/timeutils.h"
+#include "webrtc/rtc_base/trace_event.h"
 
 namespace webrtc {
 
 namespace {
 
+std::string TraceNameFromStatsTypeAndMemberName(const char* stats_type,
+                                                const char* member_name) {
+  std::ostringstream oss;

[tommi, 2017/07/12 13:56:49]

please don't use stringstream for anything else than debug logging. Use
StringPrintf instead.

[ehmaldonado_webrtc, 2017/07/12 15:27:19]

What about something like this?
It looks like StringPrintf is a Chromium function, I couldn't find a definition
in WebRTC.

+  oss << stats_type << '.' << member_name;
+  return oss.str();
+}
+
 std::string RTCCertificateIDFromFingerprint(const std::string& fingerprint) {
   return "RTCCertificate_" + fingerprint;
 }
@@ -751,6 +759,17 @@ void RTCStatsCollector::AddPartialResults_s(
     channel_name_pairs_.reset();
     track_media_info_map_.reset();
     track_to_id_.clear();
+    for (const RTCStats& stats : *cached_report_) {
+      for (const RTCStatsMemberInterface* member : stats.Members()) {
+        if (member->is_defined()) {
+          TRACE_EVENT_INSTANT2("webrtc_stats",
+                               TraceNameFromStatsTypeAndMemberName(
+                                   stats.type(), member->name()).c_str(),
+                               "value", member->ValueToString(),
+                               "id", stats.id());
+        }
+      }
+    }
     DeliverCachedReport();
   }
 }