Use request start time for estimating network quality.

net/base/network_quality_estimator.cc

Index: net/base/network_quality_estimator.cc
diff --git a/net/base/network_quality_estimator.cc b/net/base/network_quality_estimator.cc
index e012a99d72fdcc752cf4e9406f8e61651315598a..710703e11a2cf1cba2367c3927b5cf0a27e46a5b 100644
--- a/net/base/network_quality_estimator.cc
+++ b/net/base/network_quality_estimator.cc
@@ -7,6 +7,7 @@
 #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"
@@ -49,7 +50,12 @@ void NetworkQualityEstimator::NotifyDataReceived(const URLRequest& request,
     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;