Expose packet loss counts from QUIC to NetworkQualityEstimator

net/base/network_quality_estimator.h

Index: net/base/network_quality_estimator.h
diff --git a/net/base/network_quality_estimator.h b/net/base/network_quality_estimator.h
index 9fa0ad1817604c0472f8e5bafb9f78b619cfe477..74100dc51addaecdb6408e261617c58bb2d85c24 100644
--- a/net/base/network_quality_estimator.h
+++ b/net/base/network_quality_estimator.h
@@ -13,6 +13,7 @@
 #include <string>
 #include <tuple>
 
+#include "base/compiler_specific.h"
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
@@ -69,9 +70,9 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   // Observes measurements of round trip time.
   class NET_EXPORT_PRIVATE RTTObserver {
    public:
-    // Will be called when a new RTT observation is available. The round trip
-    // time is specified in milliseconds. The time when the observation was
-    // taken and the source of the observation are provided.
+    // OnRTTObservation will be called when a new RTT observation is available.
+    // The round trip time is specified in milliseconds. The time when the
+    // observation was taken and the source of the observation are provided.
     virtual void OnRTTObservation(int32_t rtt_ms,
                                   const base::TimeTicks& timestamp,
                                   ObservationSource source) = 0;
@@ -101,6 +102,37 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
     DISALLOW_COPY_AND_ASSIGN(ThroughputObserver);
   };
 
+  // Observes measurements of packet counts.
+  class NET_EXPORT_PRIVATE PacketCountObserver {
+   public:
+    // OnIncrementalPacketCountObservation will be called when incremental
+    // packet counts are available. |packets_missing| is the number of packets
+    // newly missing, but they may be received later and will be counted as out
+    // of order. |packets_received_in_order| is the number of packets received
+    // in order. |packets_received_out_of_order| is the number of packets
+    // received out of order.
+
+    // An example:
+    // Last observation after packet #1. Packets #5 and #6 are received:
+    //   missing = 3, in_order = 2, out_of_order = 0.

[Jana, 2016/03/12 03:11:28]

Inferring missing packets is something that QUIC/TCP's loss detection mechanisms
do, and simply inferring 2, 3, and 4 as missing here would be aggressive, and
may not be in line with what the transport underneath is doing. For instance,
what if immediately after 6 is received, 2, 3, 4 are received?

+
+    // Last observation after packet #6. Packet #3 received:
+    //   missing = 0, in_order = 0, out_of_order = 1.
+    virtual void OnIncrementalPacketCountObservation(
+        size_t packets_missing,
+        size_t packets_received_in_order,
+        size_t packets_received_out_of_order,
+        const base::TimeTicks& timestamp,
+        ObservationSource source) = 0;
+
+   protected:
+    PacketCountObserver() {}
+    virtual ~PacketCountObserver() {}
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(PacketCountObserver);
+  };
+
   // Creates a new NetworkQualityEstimator.
   // |variation_params| is the map containing all field trial parameters
   // related to NetworkQualityEstimator field trial.
@@ -131,13 +163,14 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   ~NetworkQualityEstimator() override;
 
   // Returns true if RTT is available and sets |rtt| to estimated RTT.
-  // Virtualized for testing. |rtt| should not be null.
-  virtual bool GetRTTEstimate(base::TimeDelta* rtt) const;
+  // Virtualized for testing. |rtt| must not be null.
+  virtual bool GetRTTEstimate(base::TimeDelta* rtt) const WARN_UNUSED_RESULT;
 
   // Returns true if downlink throughput is available and sets |kbps| to
   // estimated downlink throughput (in kilobits per second).
-  // Virtualized for testing. |kbps| should not be null.
-  virtual bool GetDownlinkThroughputKbpsEstimate(int32_t* kbps) const;
+  // Virtualized for testing. |kbps| must not be null.
+  virtual bool GetDownlinkThroughputKbpsEstimate(int32_t* kbps) const
+      WARN_UNUSED_RESULT;
 
   // Notifies NetworkQualityEstimator that the response header of |request| has
   // been received.
@@ -149,23 +182,29 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
 
   // Returns true if median RTT is available and sets |rtt| to the median of
   // RTT observations since |begin_timestamp|.
-  // Virtualized for testing. |rtt| should not be null.
+  // Virtualized for testing. |rtt| must not be null.
   virtual bool GetRecentMedianRTT(const base::TimeTicks& begin_timestamp,
-                                  base::TimeDelta* rtt) const;
+                                  base::TimeDelta* rtt) const
+      WARN_UNUSED_RESULT;
 
   // Returns true if median downstream throughput is available and sets |kbps|
   // to the median of downstream throughput (in kilobits per second)
   // observations since |begin_timestamp|. Virtualized for testing. |kbps|
-  // should not be null.
+  // must not be null.
   virtual bool GetRecentMedianDownlinkThroughputKbps(
       const base::TimeTicks& begin_timestamp,
-      int32_t* kbps) const;
+      int32_t* kbps) const WARN_UNUSED_RESULT;
 
   // SocketPerformanceWatcherFactory implementation:
   scoped_ptr<SocketPerformanceWatcher> CreateSocketPerformanceWatcher(
       const Protocol protocol) override;
   void OnUpdatedRTTAvailable(const Protocol protocol,
                              const base::TimeDelta& rtt) override;
+  void OnIncrementalPacketCountAvailable(
+      Protocol protocol,
+      size_t packets_missing,
+      size_t packets_received_in_order,
+      size_t packets_received_out_of_order) override;
 
   // Adds |rtt_observer| to the list of round trip time observers. Must be
   // called on the IO thread.
@@ -183,6 +222,14 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   // is on the list of observers. Must be called on the IO thread.
   void RemoveThroughputObserver(ThroughputObserver* throughput_observer);
 
+  // Adds |packet_count_observer| to the list of packet count observers. Must be
+  // called on the IO thread.
+  void AddPacketCountObserver(PacketCountObserver* packet_count_observer);
+
+  // Removes |packet_count_observer| from the list of packet count observers if
+  // it is on the list of observers. Must be called on the IO thread.
+  void RemovePacketCountObserver(PacketCountObserver* packet_count_observer);
+
  protected:
   // NetworkID is used to uniquely identify a network.
   // For the purpose of network quality estimation and caching, a network is
@@ -389,11 +436,10 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
 
     // Returns true iff the |percentile| value of the observations in this
     // buffer is available. Sets |result| to the computed |percentile|
-    // value among all observations since |begin_timestamp|. If the value is
-    // unavailable, false is returned and |result| is not modified. Percentile
-    // value is unavailable if all the values in observation buffer are older
-    // than |begin_timestamp|.
-    // |result| must not be null.
+    // value among all observations since |begin_timestamp| (inclusive). If the
+    // value is unavailable, false is returned and |result| is not modified.
+    // Percentile value is unavailable if all the values in observation buffer
+    // are older than |begin_timestamp|. |result| must not be null.
     bool GetPercentile(const base::TimeTicks& begin_timestamp,
                        ValueType* result,
                        int percentile) const;
@@ -504,10 +550,11 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   // returned estimate with 0.9 probability. Similarly, network is expected to
   // be slower than the returned estimate with 0.1 probability.
   base::TimeDelta GetRTTEstimateInternal(const base::TimeTicks& begin_timestamp,
-                                         int percentile) const;
+                                         int percentile) const
+      WARN_UNUSED_RESULT;
   int32_t GetDownlinkThroughputKbpsEstimateInternal(
       const base::TimeTicks& begin_timestamp,
-      int percentile) const;
+      int percentile) const WARN_UNUSED_RESULT;
 
   // Returns the current network ID checking by calling the platform APIs.
   // Virtualized for testing.
@@ -520,6 +567,13 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
 
   void NotifyObserversOfThroughput(const ThroughputObservation& observation);
 
+  void NotifyObserversOfIncrementalPacketCount(
+      size_t packets_missing,
+      size_t packets_received_in_order,
+      size_t packets_received_out_of_order,
+      const base::TimeTicks& timestamp,
+      ObservationSource source);
+
   // Records the UMA related to RTT.
   void RecordRTTUMA(int32_t estimated_value_msec,
                     int32_t actual_value_msec) const;
@@ -545,6 +599,14 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   void RecordExternalEstimateProviderMetrics(
       NQEExternalEstimateProviderStatus status) const;
 
+  // Gets the ObservationSource that corresponds to the given |protocol|,
+  // updates |observation_source| and returns true. If the corresponding
+  // ObservationSource is unknown, false is returned and |observation_source| is
+  // not modified.
+  bool GetObservationSourceForProtocol(
+      Protocol protocol,
+      ObservationSource* observation_source) const;
+
   // Determines if the requests to local host can be used in estimating the
   // network quality. Set to true only for tests.
   const bool allow_localhost_requests_;
@@ -591,9 +653,11 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   // system APIs. May be NULL.
   const scoped_ptr<ExternalEstimateProvider> external_estimate_provider_;
 
-  // Observer lists for round trip times and throughput measurements.
+  // Observer lists for round trip times, throughput and packet count
+  // measurements.
   base::ObserverList<RTTObserver> rtt_observer_list_;
   base::ObserverList<ThroughputObserver> throughput_observer_list_;
+  base::ObserverList<PacketCountObserver> packet_count_observer_list_;
 
   base::ThreadChecker thread_checker_;