Expose transport RTT estimate from Network Quality Estimator (NQE)

net/nqe/network_quality_estimator.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_NQE_NETWORK_QUALITY_ESTIMATOR_H_
 #define NET_NQE_NETWORK_QUALITY_ESTIMATOR_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 323 matching lines @@
   void RemoveNetworkQualitiesCacheObserver(
       nqe::internal::NetworkQualityStore::NetworkQualitiesCacheObserver*
           observer);
 
   // Called when the persistent prefs have been read. |read_prefs| contains the
   // parsed prefs as a map between NetworkIDs and CachedNetworkQualities.
   void OnPrefsRead(
       const std::map<nqe::internal::NetworkID,
                      nqe::internal::CachedNetworkQuality> read_prefs);
 
+  // Returns the current transport RTT estimate. If the estimate is unavailable,
+  // the returned optional value is null.

[RyanSturm, 2017/05/25 23:05:50]

nit:s/value is null/has no value/

[tbansal1, 2017/05/26 01:29:28]

Done.

+  base::Optional<base::TimeDelta> GetTransportRTT() const;
+
  protected:
   // A protected constructor for testing that allows setting the value of
   // |add_default_platform_observations_|.
   NetworkQualityEstimator(
       std::unique_ptr<ExternalEstimateProvider> external_estimates_provider,
       const std::map<std::string, std::string>& variation_params,
       bool use_local_host_requests_for_tests,
       bool use_smaller_responses_for_tests,
       bool add_default_platform_observations,
       const NetLogWithSource& net_log);
@@ skipping 435 matching lines @@
       disallowed_observation_sources_for_transport_;
 
   base::WeakPtrFactory<NetworkQualityEstimator> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkQualityEstimator);
 };
 
 }  // namespace net
 
 #endif  // NET_NQE_NETWORK_QUALITY_ESTIMATOR_H_