Add histograms for data usage

chrome/browser/android/data_usage/external_data_use_observer.cc

Index: chrome/browser/android/data_usage/external_data_use_observer.cc
diff --git a/chrome/browser/android/data_usage/external_data_use_observer.cc b/chrome/browser/android/data_usage/external_data_use_observer.cc
index 94e9e0607003bfd3c5f19c56a7f22dae867d9a14..8921b62c002da4b95a7236755e2c33078fdb2439 100644
--- a/chrome/browser/android/data_usage/external_data_use_observer.cc
+++ b/chrome/browser/android/data_usage/external_data_use_observer.cc
@@ -205,6 +205,9 @@ void ExternalDataUseObserver::OnReportDataUseDone(bool success) {
     RecordDataUsageReportSubmission(DATAUSAGE_REPORT_SUBMISSION_FAILED,
                                     pending_report_bytes_);
   }
+  UMA_HISTOGRAM_TIMES(

[Raj, 2016/01/13 23:33:51]

Here again, the duration includes 2 thread hops.
Should we need to only log pure report submission timing ?
Or thread hop is negligible ? 

[tbansal1, 2016/01/14 06:59:55]

Delay due to thread hop can sometimes be large. I think here it is okay to
include thread hop because EDUO can submit next report only when the previous
report callback has come back. So, we are measuring the right metric.

In the other place, you were adding an extra unnecessary thread hop just for
measuring purpose, so that was not measuring the right metric.

+      "DataUsage.Perf.ReportSubmissionDuration",
+      base::TimeTicks::Now() - last_data_report_submitted_ticks_);
 
   last_data_report_submitted_ticks_ = base::TimeTicks();
   pending_report_bytes_ = 0;
@@ -212,6 +215,13 @@ void ExternalDataUseObserver::OnReportDataUseDone(bool success) {
   SubmitBufferedDataUseReport(false);
 }
 
+void ExternalDataUseObserver::OnFetchMatchingRulesDone() const {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  DCHECK(!last_matching_rules_fetch_time_.is_null());
+  UMA_HISTOGRAM_TIMES("DataUsage.Perf.MatchingRuleFetchDuration",
+                      base::TimeTicks::Now() - last_matching_rules_fetch_time_);
+}
+
 #if defined(OS_ANDROID)
 void ExternalDataUseObserver::OnApplicationStateChange(
     base::android::ApplicationState new_state) {