Add functionality for embedders to configure NQE

components/cronet/android/cronet_url_request_context_adapter.cc

Index: components/cronet/android/cronet_url_request_context_adapter.cc
diff --git a/components/cronet/android/cronet_url_request_context_adapter.cc b/components/cronet/android/cronet_url_request_context_adapter.cc
index 2a252b4386e3e74e1777460d265cf7e4390ad4e0..be7c532e38dfb0c0d925251cd7df8d07c8b8e002 100644
--- a/components/cronet/android/cronet_url_request_context_adapter.cc
+++ b/components/cronet/android/cronet_url_request_context_adapter.cc
@@ -674,18 +674,43 @@ void CronetURLRequestContextAdapter::InitializeOnNetworkThread(
 
   if (config->enable_network_quality_estimator) {
     DCHECK(!network_quality_estimator_);
-    std::map<std::string, std::string> variation_params;
+
+    // NetworkQualityEstimator experiment dictionary name.
+    const char kNetworkQualityEstimatorFieldTrialName[] =

[mgersh, 2017/05/02 18:06:49]

Instead of duplicating this here, you could make it accessible from
url_request_context_config.h.

[tbansal1, 2017/06/28 14:19:54]

Obsolete.

+        "NetworkQualityEstimator";
+
+    // Network quality estimator configuration params.
+    std::map<std::string, std::string> network_quality_estimator_options;
+    const base::DictionaryValue* nqe_args = nullptr;
+
+    if (effective_experimental_options_ &&
+        effective_experimental_options_->GetDictionary(
+            kNetworkQualityEstimatorFieldTrialName, &nqe_args)) {

[xunjieli, 2017/05/02 17:56:34]

Can we move the parsing of NQE options to url_request_context_config.cc? The
reason is that we want to detect any unrecognized options at one place, so
Cronet's NetLog dumps can have a full picture of what's in effect.

[tbansal1, 2017/06/28 14:19:54]

Done.

+      for (base::DictionaryValue::Iterator it(*nqe_args); !it.IsAtEnd();
+           it.Advance()) {
+        std::string value_string;
+        bool value_string_available;
+        value_string_available = it.value().GetAsString(&value_string);
+        DCHECK(value_string_available);
+        network_quality_estimator_options.emplace(it.key(), value_string);
+      }
+    }
+
     // Configure network quality estimator: Specify the algorithm that should
-    // be used for computing the effective connection type. The algorithm
-    // is specified using the key-value pairs defined in
-    // //net/nqe/network_quality_estimator.cc.
-    // TODO(tbansal): Investigate a more robust way of configuring the network
-    // quality estimator.
-    variation_params["effective_connection_type_algorithm"] =
-        "TransportRTTOrDownstreamThroughput";
+    // be used for computing the effective connection type if it has not been
+    // specified by the embedder. The algorithm is specified using the
+    // key-value pairs defined in //net/nqe/network_quality_estimator.cc.
+    if (network_quality_estimator_options.find(
+            "effective_connection_type_algorithm") ==
+        network_quality_estimator_options.end()) {
+      network_quality_estimator_options.emplace(
+          "effective_connection_type_algorithm",
+          "TransportRTTOrDownstreamThroughput");
+    }
     network_quality_estimator_ = base::MakeUnique<net::NetworkQualityEstimator>(
-        std::unique_ptr<net::ExternalEstimateProvider>(), variation_params,
-        false, false, g_net_log.Get().net_log());
+        std::unique_ptr<net::ExternalEstimateProvider>(),
+        network_quality_estimator_options, false, false,
+        g_net_log.Get().net_log());
     // Set the socket performance watcher factory so that network quality
     // estimator is notified of socket performance metrics from TCP and QUIC.
     context_builder.set_socket_performance_watcher_factory(