Record the time since Chromium is in background for background data use

components/data_use_measurement/content/data_use_measurement_unittest.cc

Index: components/data_use_measurement/content/data_use_measurement_unittest.cc
diff --git a/components/data_use_measurement/content/data_use_measurement_unittest.cc b/components/data_use_measurement/content/data_use_measurement_unittest.cc
index 29b5717f9330b1f04139cc77f9a5e59f897ff706..6700ec134bee7e1a9f10f34120f9e1fadb8fa868 100644
--- a/components/data_use_measurement/content/data_use_measurement_unittest.cc
+++ b/components/data_use_measurement/content/data_use_measurement_unittest.cc
@@ -211,6 +211,54 @@ TEST_F(DataUseMeasurementTest, AppStateUnknown) {
         "DataUse.TrafficSize.User.Downstream.Background." + kConnectionType, 1);
   }
 }
+
+TEST_F(DataUseMeasurementTest, TimeOfBackgroundDownstreamBytes) {
+  base::HistogramTester histogram_tester;
+  std::unique_ptr<net::URLRequest> request = CreateTestRequest(false);
+  data_use_measurement_.OnBeforeURLRequest(request.get());
+
+  {
+    base::HistogramTester histogram_tester;
+    data_use_measurement()->OnApplicationStateChange(
+        base::android::APPLICATION_STATE_HAS_RUNNING_ACTIVITIES);
+    data_use_measurement_.OnNetworkBytesSent(*request, 100);
+    data_use_measurement_.OnNetworkBytesReceived(*request, 1000);
+    data_use_measurement_.OnNetworkBytesSent(*request, 200);
+    data_use_measurement_.OnNetworkBytesReceived(*request, 2000);
+    histogram_tester.ExpectTotalCount("DataUse.BackgroundDownstreamBytes.User",
+                                      0);
+    histogram_tester.ExpectTotalCount(
+        "DataUse.BackgroundDownstreamFirstRead.User", 0);
+  }
+
+  {
+    base::HistogramTester histogram_tester;
+    data_use_measurement()->OnApplicationStateChange(

[Not at Google. Contact bengr, 2016/10/14 23:10:57]

Would suggest improving this test by adding request[s] between this and a prior
APPLICATION_STATE_HAS_RUNNING_ACTIVITIES. That way test will also confirm that
requests made before APPLICATION_STATE_HAS_STOPPED_ACTIVITIES are not counted.

[Raj, 2016/10/15 19:36:14]

Done.

+        base::android::APPLICATION_STATE_HAS_STOPPED_ACTIVITIES);
+    data_use_measurement_.OnNetworkBytesSent(*request, 100);
+    data_use_measurement_.OnNetworkBytesReceived(*request, 1000);
+    data_use_measurement_.OnNetworkBytesSent(*request, 200);
+    data_use_measurement_.OnNetworkBytesReceived(*request, 2000);
+    histogram_tester.ExpectTotalCount("DataUse.BackgroundDownstreamBytes.User",
+                                      3000);
+    histogram_tester.ExpectTotalCount(
+        "DataUse.BackgroundDownstreamFirstRead.User", 1);
+  }
+
+  {
+    base::HistogramTester histogram_tester;

[Not at Google. Contact bengr, 2016/10/14 23:10:57]

This and the first test seem exactly the same. Did you mean to add a test for
DataUse.BackgroundDownstreamFirstRead.System?

This is not testing for the time value in
DataUse.BackgroundDownstreamFirstRead.*. You could do it by using helper methods
OnApplicationStateChangeInternal() and ReportDataUseUMAInternal() which
explicitly take Time::Now() as an argument. However, I don't feel strongly about
the value of adding this test, and so leave it to you to decide.

[Raj, 2016/10/15 19:36:15]

Added a test for DataUse.BackgroundDownstreamFirstRead.System.

Yes. I do not feel strongly either.
This test just checks that no UMA is recorded when app is in foreground (after
foreground-background) transitions.

+    data_use_measurement()->OnApplicationStateChange(
+        base::android::APPLICATION_STATE_HAS_RUNNING_ACTIVITIES);
+    data_use_measurement_.OnNetworkBytesSent(*request, 100);
+    data_use_measurement_.OnNetworkBytesReceived(*request, 1000);
+    data_use_measurement_.OnNetworkBytesSent(*request, 200);
+    data_use_measurement_.OnNetworkBytesReceived(*request, 2000);
+    histogram_tester.ExpectTotalCount("DataUse.BackgroundDownstreamBytes.User",
+                                      0);
+    histogram_tester.ExpectTotalCount(
+        "DataUse.BackgroundDownstreamFirstRead.User", 0);
+  }
+}
 #endif
 
 }  // namespace data_use_measurement