Add tracing to measure the entire time it takes to satisfy a getStats request.

content/renderer/media/rtc_peer_connection_handler.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/media/rtc_peer_connection_handler.h"
 
 #include <string>
 #include <utility>
 #include <vector>
 
@@ skipping 215 matching lines @@
  private:
   blink::WebRTCVoidRequest webkit_request_;
   SessionDescriptionRequestTracker tracker_;
 };
 
 // Class mapping responses from calls to libjingle
 // GetStats into a blink::WebRTCStatsCallback.
 class StatsResponse : public webrtc::StatsObserver {
  public:
   explicit StatsResponse(const scoped_refptr<LocalRTCStatsRequest>& request)
-      : request_(request.get()), response_(request_->createResponse().get()) {}
+      : request_(request.get()), response_(request_->createResponse().get()) {
+    // Measure the overall time it takes to satisfy a getStats request.
+    TRACE_EVENT_ASYNC_BEGIN0("webrtc", "getStats_Native", this);
+  }
 
   virtual void OnComplete(
       const std::vector<webrtc::StatsReport>& reports) OVERRIDE {
     TRACE_EVENT0("webrtc", "StatsResponse::OnComplete")

[no longer working on chromium, 2014/06/02 11:03:21]

do we still need this TRACE_EVENT0?

[tommi (sloooow) - chröme, 2014/06/02 11:27:48]

Yes, this one is still valuable.  It covers the callback as well, so it
currently is good to have to understand which portions of the wall-clock-time
have to do with adding reports and which have to do with calling into blink.

     for (std::vector<webrtc::StatsReport>::const_iterator it = reports.begin();
          it != reports.end(); ++it) {
       if (it->values.size() > 0) {
         AddReport(*it);
       }
     }
+
+    // Record the getSync operation as done before calling into Blink so that
+    // we don't skew the perf measurements of the native code with whatever the
+    // callback might be doing.
+    TRACE_EVENT_ASYNC_END0("webrtc", "getStats_Native", this);
+
     request_->requestSucceeded(response_);
   }
 
  private:
   void AddReport(const webrtc::StatsReport& report) {
     int idx = response_->addReport(blink::WebString::fromUTF8(report.id),
                                    blink::WebString::fromUTF8(report.type),
                                    report.timestamp);
     for (webrtc::StatsReport::Values::const_iterator value_it =
          report.values.begin();
@@ skipping 604 matching lines @@
   webrtc::SessionDescriptionInterface* native_desc =
       dependency_factory_->CreateSessionDescription(type, sdp, error);
 
   LOG_IF(ERROR, !native_desc) << "Failed to create native session description."
                               << " Type: " << type << " SDP: " << sdp;
 
   return native_desc;
 }
 
 }  // namespace content