NQE: Add Transport RTT based GetECT algorithm

net/nqe/network_quality_estimator.h

Index: net/nqe/network_quality_estimator.h
diff --git a/net/nqe/network_quality_estimator.h b/net/nqe/network_quality_estimator.h
index b7fc886b5ab558f41fe1ed6a1e364c9bfb0e5fb6..62d5f7ebf7517f2270e57034a168e954dc3c2024 100644
--- a/net/nqe/network_quality_estimator.h
+++ b/net/nqe/network_quality_estimator.h
@@ -372,6 +372,7 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   // connection type.
   enum class EffectiveConnectionTypeAlgorithm {
     HTTP_RTT_AND_DOWNSTREAM_THROUGHOUT = 0,
+    TRANSPORT_RTT_OR_DOWNSTREAM_THROUGHOUT,
     EFFECTIVE_CONNECTION_TYPE_ALGORITHM_LAST
   };
 
@@ -485,6 +486,14 @@ class NET_EXPORT_PRIVATE NetworkQualityEstimator
   GetRecentEffectiveConnectionTypeHttpRTTAndDownstreamThroughput(
       const base::TimeTicks& start_time) const;
 
+  // Returns the effective type of the current connection based on only the
+  // samples observed after |start_time|. Uses transport RTT and downstream
+  // throughput to compute the effective connection type, and requires at least
+  // one of them to have a valid value.
+  EffectiveConnectionType
+  GetRecentEffectiveConnectionTypeTransportRTTOrDownstreamThroughput(
+      const base::TimeTicks& start_time) const;
+
   // Values of external estimate provider status. This enum must remain
   // synchronized with the enum of the same name in
   // metrics/histograms/histograms.xml.