Create a DataUseRecorder instance for each page load in Chrome.

components/data_use_measurement/core/data_use_recorder.h

 // Copyright 2016 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 COMPONENTS_DATA_USE_MEASUREMENT_CORE_DATA_USE_RECORDER_H_
 #define COMPONENTS_DATA_USE_MEASUREMENT_CORE_DATA_USE_RECORDER_H_
 
 #include <stdint.h>
 
 #include "base/containers/hash_tables.h"
@@ skipping 12 matching lines @@
 // can make multiple URLRequests, so there is a one:many relationship between
 // DataUseRecorders and URLRequests. Data used by each URLRequest will be
 // tracked by exactly one DataUseRecorder.
 class DataUseRecorder {
  public:
   DataUseRecorder();
   ~DataUseRecorder();
 
   // Returns the actual data used by the entity being tracked.
   DataUse& data_use() { return data_use_; }
+  base::hash_set<net::URLRequest*>& pending_url_requests() {

[RyanSturm, 2016/11/29 20:33:00]

Can this return a const ref and be a const method?

[Not at Google. Contact bengr, 2016/11/30 00:21:16]

Done.

+    return pending_url_requests_;
+  }
+  const net::URLRequest* main_url_request() { return main_url_request_; }

[RyanSturm, 2016/11/29 20:33:00]

const method

[Not at Google. Contact bengr, 2016/11/30 00:21:16]

Done.

+
+  void set_main_url_request(const net::URLRequest* request) {
+    main_url_request_ = request;
+  }
 
   // Returns whether data use is complete and no additional data can be used
   // by the entity tracked by this recorder. For example,
   bool IsDataUseComplete();
 
+  void AddPendingURLRequest(net::URLRequest* request);
+  //  void RemovePendingURLRequest(net::URLRequest* request);

[RyanSturm, 2016/11/29 20:33:00]

This comment should be replaced by a description, and add a comment to
AddPendingURLRequest

[Not at Google. Contact bengr, 2016/11/30 00:21:16]

Done.

+  void RemoveAllPendingURLRequests();
+
+  // Returns whether there are any pending URLRequests whose data use is tracked
+  // by this DataUseRecorder.
+  bool HasPendingURLRequest(net::URLRequest* request);
+
+  // Merge another DataUseRecorder to this instance.
+  void MergeFrom(DataUseRecorder* other);
+
+ private:
+  friend class DataUseAscriber;
+
   // Methods for tracking data use sources. These sources can initiate
   // URLRequests directly or indirectly. The entity whose data use is being
   // tracked by this recorder may comprise of sub-entities each of which use
   // network data. These helper methods help track these sub-entities.
   // A recorder will not be marked as having completed data use as long as it
   // has pending data sources.
   void AddPendingDataSource(void* source);
   bool HasPendingDataSource(void* source);
   void RemovePendingDataSource(void* source);
 
-  // Returns whether there are any pending URLRequests whose data use is tracked
-  // by this DataUseRecorder.
-  bool HasPendingURLRequest(const net::URLRequest* request);
-
-  // Method to merge another DataUseRecorder to this instance.
-  void MergeWith(DataUseRecorder* other);
-
- private:
-  friend class DataUseAscriber;
-
   // Network Delegate methods:
   void OnBeforeUrlRequest(net::URLRequest* request);
   void OnUrlRequestDestroyed(net::URLRequest* request);
   void OnNetworkBytesSent(net::URLRequest* request, int64_t bytes_sent);
   void OnNetworkBytesReceived(net::URLRequest* request, int64_t bytes_received);
 
   // Pending URLRequests whose data is being tracked by this DataUseRecorder.
-  base::hash_set<const net::URLRequest*> pending_url_requests_;
+  base::hash_set<net::URLRequest*> pending_url_requests_;
 
   // Data sources other than URLRequests, whose data is being tracked by this
   // DataUseRecorder.
   base::hash_set<const void*> pending_data_sources_;
 
+  // For page loads this is main frame URLRequest.

[RyanSturm, 2016/11/29 20:33:00]

nit: change this to something like: The main frame URLRequest for page loads.
Null if this is not tracking a page load.

[Not at Google. Contact bengr, 2016/11/30 00:21:16]

Done.

+  const net::URLRequest* main_url_request_;
+
   // The network data use measured by this DataUseRecorder.
   DataUse data_use_;
 
   DISALLOW_COPY_AND_ASSIGN(DataUseRecorder);
 };
 
 }  // namespace data_use_measurement
 
 #endif  // COMPONENTS_DATA_USE_MEASUREMENT_CORE_DATA_USE_RECORDER_H_