Store network quality samples so we can compute percentiles.

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..43285e06187fc0e2e6622ac0750324801bd35f5d 100644
--- a/net/base/network_quality_estimator.cc
+++ b/net/base/network_quality_estimator.cc
@@ -6,6 +6,7 @@
 
 #include <string>
 
+#include "base/logging.h"
 #include "base/metrics/histogram.h"
 #include "net/base/net_util.h"
 #include "net/base/network_quality.h"
@@ -35,18 +36,23 @@ NetworkQualityEstimator::~NetworkQualityEstimator() {
   NetworkChangeNotifier::RemoveConnectionTypeObserver(this);
 }
 
-void NetworkQualityEstimator::NotifyDataReceived(const URLRequest& request,
-                                                 int64_t prefilter_bytes_read) {
+void NetworkQualityEstimator::NotifyDataReceived(
+    const URLRequest& request,
+    int64_t cummulative_prefilter_bytes_read,
+    int64_t prefiltered_bytes_read) {
   DCHECK(thread_checker_.CalledOnValidThread());
-  DCHECK_GT(prefilter_bytes_read, 0);
+  DCHECK_GT(cummulative_prefilter_bytes_read, 0);
+  DCHECK_GT(prefiltered_bytes_read, 0);
 
   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())
+      request.response_info().response_time.is_null() || request.was_cached() ||
+      request.creation_time() < last_connection_change_) {
     return;
+  }
 
   base::TimeTicks now = base::TimeTicks::Now();
   base::TimeDelta request_duration = now - request.creation_time();
@@ -58,16 +64,22 @@ void NetworkQualityEstimator::NotifyDataReceived(const URLRequest& request,
   if (request_duration < fastest_RTT_since_last_connection_change_)
     fastest_RTT_since_last_connection_change_ = request_duration;
 
+  // Only add RTT sample if this is the first read for this response.
+  if (cummulative_prefilter_bytes_read == prefiltered_bytes_read)
+    rtt_msec_.AddSample(request_duration.InMilliseconds());
+
   // Ignore tiny transfers which will not produce accurate rates.
   // Ignore short duration transfers.
-  if (prefilter_bytes_read >= kMinTransferSizeInBytes &&
+  if (cummulative_prefilter_bytes_read >= kMinTransferSizeInBytes &&
       request_duration >=
-          base::TimeDelta::FromMicroseconds(kMinRequestDurationMicroseconds) &&
-      request.creation_time() > last_connection_change_) {
-    uint64_t kbps = static_cast<uint64_t>(prefilter_bytes_read * 8 * 1000 /
-                                          request_duration.InMicroseconds());
+          base::TimeDelta::FromMicroseconds(kMinRequestDurationMicroseconds)) {
+    uint64_t kbps =
+        static_cast<uint64_t>(cummulative_prefilter_bytes_read * 8 * 1000 /
+                              request_duration.InMicroseconds());
     if (kbps > peak_kbps_since_last_connection_change_)
       peak_kbps_since_last_connection_change_ = kbps;
+
+    kbps_.AddSample(kbps);
   }
 }
 
@@ -160,7 +172,7 @@ void NetworkQualityEstimator::OnConnectionTypeChanged(
   current_connection_type_ = type;
 }
 
-NetworkQuality NetworkQualityEstimator::GetEstimate() const {
+NetworkQuality NetworkQualityEstimator::GetPeakEstimate() const {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   if (!bytes_read_since_last_connection_change_) {
@@ -175,4 +187,29 @@ NetworkQuality NetworkQualityEstimator::GetEstimate() const {
                         peak_kbps_since_last_connection_change_, 0.1);

[mmenke, 2015/06/03 18:31:39]

This seems a bit silly.  Suggest just always returning 0, until we actually have
a meaningful value.

[tbansal1, 2015/06/05 01:50:08]

Done.

 }
 
+NetworkQualityEstimator::Sample::Sample(int value)
+    : value_(value), timestamp_(base::TimeTicks::Now()) {
+  DCHECK_GE(value_, 0);
+}
+
+NetworkQualityEstimator::Sample::~Sample() {
+}
+
+NetworkQualityEstimator::RingBuffer::RingBuffer() {
+  DCHECK_GT(kMaximumSamples, 0U);

[mmenke, 2015/06/03 18:31:39]

If you think this is necessary, should use static_assert up where you declare
the variable, rather than a runtime assertion.

[tbansal1, 2015/06/05 01:50:08]

Done.

+}
+
+NetworkQualityEstimator::RingBuffer::~RingBuffer() {
+}
+
+void NetworkQualityEstimator::RingBuffer::AddSample(int value) {
+  DCHECK_LE(samples_.size(), kMaximumSamples);
+  // Pop the oldest element if the buffer is already full.
+  if (samples_.size() >= kMaximumSamples)
+    samples_.pop_front();
+
+  samples_.push_back(Sample(value));
+  DCHECK_LE(samples_.size(), kMaximumSamples);
+}
+
 }  // namespace net