Support for identifying traffic type in data use ascriber

components/data_use_measurement/core/data_use.h

Index: components/data_use_measurement/core/data_use.h
diff --git a/components/data_use_measurement/core/data_use.h b/components/data_use_measurement/core/data_use.h
index 18e706dc6d4d40b45e151073bcb3d8df5c560f66..cc1d87a242ef923a12490d633be662130f12e32b 100644
--- a/components/data_use_measurement/core/data_use.h
+++ b/components/data_use_measurement/core/data_use.h
@@ -18,7 +18,21 @@ namespace data_use_measurement {
 // Class to store total network data used by some entity.
 class DataUse {
  public:
-  DataUse();
+  enum TrafficType {

[tbansal1, 2017/05/12 15:59:58]

can this be enum class?
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-dev/Q5WmkAImanc

[rajendrant, 2017/05/16 00:50:08]

Done.

+    // Unknown.
+    UNKNOWN,

[tbansal1, 2017/05/12 15:59:58]

May be add a TODO to record metrics on the distribution of traffic type. This
would be useful to figure out if there are lot of samples in UNKNOWN or
SERVICE_WORKER buckets (which are both bad).

[rajendrant, 2017/05/16 00:50:08]

Done.

+
+    // User initiated traffic.
+    USER_TRAFFIC,
+
+    // Chrome services.
+    SERVICES,
+
+    // Fetch from ServiceWorker.
+    SERVICE_WORKER,
+  };
+
+  DataUse(TrafficType traffic_type);

[tbansal1, 2017/05/12 15:59:58]

explicit

[rajendrant, 2017/05/16 00:50:08]

Done.

   DataUse(const DataUse& other);
   ~DataUse();
 
@@ -39,11 +53,14 @@ class DataUse {
 
   int64_t total_bytes_sent() const { return total_bytes_sent_; }
 
+  TrafficType traffic_type() { return traffic_type_; }

[tbansal1, 2017/05/12 15:59:58]

const function

[rajendrant, 2017/05/16 00:50:08]

Done.

+
  private:
   friend class DataUseRecorder;

[tbansal1, 2017/05/12 15:59:58]

TODO to remove this friend.
This probably means that DataUseRecorder is writing to the private members of
this class. This makes it difficult to understand how this class interacts with
other classes.

[rajendrant, 2017/05/16 00:50:08]

Done.

 
   GURL url_;
   std::string description_;
+  const TrafficType traffic_type_;
 
   int64_t total_bytes_sent_;
   int64_t total_bytes_received_;

[tbansal1, 2017/05/12 15:59:58]

May be add a TODO to add thread checker.

[tbansal1, 2017/05/12 15:59:58]

DISALLOW_COPY_AND_ASSIGN
or override the assignment operator.

[rajendrant, 2017/05/16 00:50:08]

Done.

[rajendrant, 2017/05/16 00:50:08]

Thread checker could be too much for this class. This is supposed to be light
object sent across data use observers.

In future this class could derive from base::SupportsUserData so that observers
can annotate arbitrary information to this. For example, Freighter could
annotate this with amortized bytes.

WDYT