Record the tab state during data use

components/data_use_measurement/core/data_use_measurement.h

Index: components/data_use_measurement/core/data_use_measurement.h
diff --git a/components/data_use_measurement/core/data_use_measurement.h b/components/data_use_measurement/core/data_use_measurement.h
index 1422ea5bd22bc45ab96f1426460635fc40112f06..779fdaf39e31d234744ee9e5d072866bfd7934e4 100644
--- a/components/data_use_measurement/core/data_use_measurement.h
+++ b/components/data_use_measurement/core/data_use_measurement.h
@@ -29,6 +29,7 @@ class URLRequest;
 
 namespace data_use_measurement {
 
+class DataUseAscriber;
 class URLRequestClassifier;
 
 // Records the data use of user traffic and various services in UMA histograms.
@@ -40,6 +41,7 @@ class URLRequestClassifier;
 class DataUseMeasurement {
  public:
   DataUseMeasurement(
+      DataUseAscriber* ascriber,
       std::unique_ptr<URLRequestClassifier> url_request_classifier,
       const metrics::UpdateUsagePrefCallbackType& metrics_data_use_forwarder);
   ~DataUseMeasurement();
@@ -74,6 +76,8 @@ class DataUseMeasurement {
   // Specifies that data is received or sent, respectively.
   enum TrafficDirection { DOWNSTREAM, UPSTREAM };
 
+  enum TabState { FOREGROUND, BACKGROUND, UNKNOWN };

[RyanSturm, 2016/12/16 16:26:10]

Is this enum really necessary, you treat it as boolean wherever you use it, so
maybe it is better to pass is_visible or is_in_foreground.

[Raj, 2016/12/16 19:59:10]

Done.

+
   // Returns the current application state (Foreground or Background). It always
   // returns Foreground if Chrome is not running on Android.
   DataUseUserData::AppState CurrentAppState() const;
@@ -128,6 +132,13 @@ class DataUseMeasurement {
       bool is_connection_cellular,
       int64_t message_size) const;
 
+  // A helper function used to record the app and tab state when data use

[RyanSturm, 2016/12/16 16:26:11]

How about "Records data use histograms split on TrafficDirection, AppState and
TabState."

[Raj, 2016/12/16 19:59:10]

Done.

+  // happens.
+  void RecordTabStateHistogram(TrafficDirection dir,
+                               DataUseUserData::AppState app_state,
+                               TabState tab_state,
+                               int64_t bytes);
+
   // Classifier for identifying if an URL request is user initiated.
   std::unique_ptr<URLRequestClassifier> url_request_classifier_;
 
@@ -137,6 +148,10 @@ class DataUseMeasurement {
   // class to support registering arbitrary observers. crbug.com/601185
   metrics::UpdateUsagePrefCallbackType metrics_data_use_forwarder_;
 
+  // DataUseAscriber used to get the attributes of data use. Not owned by

[RyanSturm, 2016/12/16 16:26:11]

I don't think you need to say "Not owned by |this|" since it is a raw pointer.

[Raj, 2016/12/16 19:59:10]

Done.

+  // |this|.
+  DataUseAscriber* ascriber_;
+
 #if defined(OS_ANDROID)
   // Application listener store the last known state of the application in this
   // field.