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 6415ee6e6d7eb36b47ab4fd568d3537283b27729..8f96aacbd97f710d9d0e4f09a8bb98bbfa3be5e2 100644
--- a/net/base/network_quality_estimator.cc
+++ b/net/base/network_quality_estimator.cc
@@ -15,6 +15,9 @@
 
 namespace net {
 
+// Maximum number of samples to hold in the SampleRingBuffer.
+const size_t NetworkQualityEstimator::SampleRingBuffer::kMaximumSamples = 500;
+
 NetworkQualityEstimator::NetworkQualityEstimator()
     : NetworkQualityEstimator(false) {
 }
@@ -36,10 +39,13 @@ 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())) ||
@@ -61,15 +67,22 @@ 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_samples_.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)) {
-    uint64_t kbps = static_cast<uint64_t>(prefilter_bytes_read * 8 * 1000 /
-                                          request_duration.InMicroseconds());
+    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_samples_.AddSample(kbps);
   }
 }
 
@@ -162,19 +175,44 @@ 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_) {
-    return NetworkQuality(fastest_RTT_since_last_connection_change_, 0,
-                          peak_kbps_since_last_connection_change_, 0);
+    return NetworkQuality(base::TimeDelta(), 0.0, 0, 0.0);
   }
   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_, 0.0, 0,
+                          0.0);
   }
-  return NetworkQuality(fastest_RTT_since_last_connection_change_, 0.1,
-                        peak_kbps_since_last_connection_change_, 0.1);
+  return NetworkQuality(fastest_RTT_since_last_connection_change_, 0.0,
+                        peak_kbps_since_last_connection_change_, 0.0);
+}
+
+NetworkQualityEstimator::Sample::Sample(int value, base::TimeTicks timestamp)
+    : value(value), timestamp(timestamp) {
+  DCHECK_GE(value, 0);
+}
+
+NetworkQualityEstimator::Sample::~Sample() {
+}
+
+NetworkQualityEstimator::SampleRingBuffer::SampleRingBuffer() {
+  static_assert(kMaximumSamples > 0U,
+                "Minimum size of sample buffer must be > 0");
+}
+
+NetworkQualityEstimator::SampleRingBuffer::~SampleRingBuffer() {
+}
+
+void NetworkQualityEstimator::SampleRingBuffer::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, base::TimeTicks::Now()));
+  DCHECK_LE(samples_.size(), kMaximumSamples);
 }
 
 }  // namespace net