Use request start time for estimating network quality.

net/base/network_quality_estimator.cc

 // Copyright 2015 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 "net/base/network_quality_estimator.h"
 
 #include <string>
 
 #include "base/metrics/histogram.h"
+#include "net/base/load_timing_info.h"
 #include "net/base/net_util.h"
 #include "net/base/network_quality.h"
 #include "net/url_request/url_request.h"
 #include "url/gurl.h"
 
 namespace net {
 
 NetworkQualityEstimator::NetworkQualityEstimator()
     : NetworkQualityEstimator(false) {
 }
@@ skipping 22 matching lines @@
 
   if (!request.url().is_valid() ||
       (!allow_localhost_requests_ && IsLocalhost(request.url().host())) ||
       !request.url().SchemeIsHTTPOrHTTPS() ||
       // Verify that response headers are received, so it can be ensured that
       // response is not cached.
       request.response_info().response_time.is_null() || request.was_cached())
     return;
 
   base::TimeTicks now = base::TimeTicks::Now();
-  base::TimeDelta request_duration = now - request.creation_time();
+
+  LoadTimingInfo load_timing_info;
+  request.GetLoadTimingInfo(&load_timing_info);
+  DCHECK_NE(load_timing_info.request_start, base::TimeTicks());

[bengr, 2015/06/01 23:23:34]

Do all requests have load timing info?

[tbansal1, 2015/06/01 23:53:36]

Seems like yes. request_start is populated in
URLRequest::Start()
https://code.google.com/p/chromium/codesearch#chromium/src/net/url_request/ur...

Also, we are reading request_start for only those requests that
are HTTP and we have received the complete response header.
So, request_start must be populated by this time.

Also,  URLRequest::ConvertRealLoadTimesToBlockingTimes() DCHECKS
if request_start is populated. This is also called after the response
headers are received.

+
+  base::TimeDelta request_duration = now - load_timing_info.request_start;
   DCHECK_GE(request_duration, base::TimeDelta());
   if (!bytes_read_since_last_connection_change_)
     fastest_RTT_since_last_connection_change_ = request_duration;
 
   bytes_read_since_last_connection_change_ = true;
   if (request_duration < fastest_RTT_since_last_connection_change_)
     fastest_RTT_since_last_connection_change_ = request_duration;
 
   // Ignore tiny transfers which will not produce accurate rates.
   // Ignore short duration transfers.
@@ skipping 106 matching lines @@
   }
   if (!peak_kbps_since_last_connection_change_) {
     return NetworkQuality(fastest_RTT_since_last_connection_change_, 0.1,
                           peak_kbps_since_last_connection_change_, 0);
   }
   return NetworkQuality(fastest_RTT_since_last_connection_change_, 0.1,
                         peak_kbps_since_last_connection_change_, 0.1);
 }
 
 }  // namespace net