Add in-memory caching of network quality estimates across network changes.

net/base/network_quality.h

 // 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.
 
 #ifndef NET_BASE_NETWORK_QUALITY_H_
 #define NET_BASE_NETWORK_QUALITY_H_
 
 #include <stdint.h>
 
 #include "base/time/time.h"
 
 namespace net {
 
 // API that is used to report the current network quality as estimated by the
 // NetworkQualityEstimator.
 struct NET_EXPORT_PRIVATE NetworkQuality {
   NetworkQuality(const base::TimeDelta& fastest_rtt,
                  double fastest_rtt_confidence,
                  uint64_t peak_throughput_kbps,
                  double peak_throughput_kbps_confidence)
       : fastest_rtt(fastest_rtt),
         fastest_rtt_confidence(fastest_rtt_confidence),
         peak_throughput_kbps(peak_throughput_kbps),
         peak_throughput_kbps_confidence(peak_throughput_kbps_confidence) {}
 
+  NetworkQuality(const NetworkQuality& other)
+      : fastest_rtt(other.fastest_rtt),
+        fastest_rtt_confidence(other.fastest_rtt_confidence),
+        peak_throughput_kbps(other.peak_throughput_kbps),
+        peak_throughput_kbps_confidence(other.peak_throughput_kbps_confidence) {
+  }
+
   ~NetworkQuality() {}
 
   // The fastest round trip time observed for the current connection.
-  const base::TimeDelta fastest_rtt;
+  base::TimeDelta fastest_rtt;
 
   // Confidence of the |fastest_rtt| estimate. Value lies between 0.0 and 1.0
   // with 0.0 being no confidence and 1.0 implying that estimates are same as
   // ground truth.
   // TODO(tbansal): Define units so values intermediate between 0.0 and 1.0 are
   // meaningful.
   const double fastest_rtt_confidence;
 
   // Peak throughput in Kbps observed for the current connection.
-  const uint64_t peak_throughput_kbps;
+  uint64_t peak_throughput_kbps;
 
   // Confidence of the |peak_throughput_kbps| estimate. Value lies between 0.0
   // and 1.0 with 0.0 being no confidence and 1.0 implying that estimates are
   // same as ground truth.
   // TODO(tbansal): Define units so values intermediate between 0.0 and 1.0 are
   // meaningful.
   const double peak_throughput_kbps_confidence;
+
+ private:
+  DISALLOW_ASSIGN(NetworkQuality);
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_NETWORK_QUALITY_H_