NQE: Record the main frame metrics at transaction start

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 663 matching lines @@
   // trial variation params. These thresholds encode how different connection
   // types behave in general. In future, complex encodings (e.g., curve
   // fitting) may be used.
   nqe::internal::NetworkQuality connection_thresholds_
       [EffectiveConnectionType::EFFECTIVE_CONNECTION_TYPE_LAST];
 
   // Typical network quality for different effective connection types.
   nqe::internal::NetworkQuality typical_network_quality_
       [EffectiveConnectionType::EFFECTIVE_CONNECTION_TYPE_LAST];
 
-  // Latest time when the headers for a main frame request were received.
+  // Time when the transaction for the last main frame request was started.
   base::TimeTicks last_main_frame_request_;
 
-  // Estimated network quality when the response headers for the last mainframe
-  // request were received.
+  // Estimated network quality when the transaction for the last main frame
+  // request was started.
   nqe::internal::NetworkQuality estimated_quality_at_last_main_frame_;
   EffectiveConnectionType effective_connection_type_at_last_main_frame_;
 
   // Estimated network quality obtained from external estimate provider when the
   // external estimate provider was last queried.
   nqe::internal::NetworkQuality external_estimate_provider_quality_;
 
   // ExternalEstimateProvider that provides network quality using operating
   // system APIs. May be NULL.
   const std::unique_ptr<ExternalEstimateProvider> external_estimate_provider_;
@@ skipping 74 matching lines @@
   nqe::internal::EventCreator event_creator_;
 
   base::WeakPtrFactory<NetworkQualityEstimator> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(NetworkQualityEstimator);
 };
 
 }  // namespace net
 
 #endif  // NET_NQE_NETWORK_QUALITY_ESTIMATOR_H_