Add histograms for observing UMA throttling effect.

components/metrics/metrics_reporting_scheduler.cc

Index: components/metrics/metrics_reporting_scheduler.cc
diff --git a/components/metrics/metrics_reporting_scheduler.cc b/components/metrics/metrics_reporting_scheduler.cc
index ab117ad01e96d3cc486840b01657b3928308e40e..21247d6694c332ada104b3a004607792225f6322 100644
--- a/components/metrics/metrics_reporting_scheduler.cc
+++ b/components/metrics/metrics_reporting_scheduler.cc
@@ -57,14 +57,6 @@ void LogMetricsInitSequence(InitSequence sequence) {
                             INIT_SEQUENCE_ENUM_SIZE);
 }
 
-void LogActualUploadInterval(TimeDelta interval) {
-  UMA_HISTOGRAM_CUSTOM_COUNTS("UMA.ActualLogUploadInterval",

[Alexei Svitkine (slow), 2016/04/08 20:07:12]

I'm not convinced we should stop logging this yet. Let's keep it for now.

[gayane -on leave until 09-2017, 2016/04/08 20:40:14]

Done.

-                             interval.InMinutes(),
-                             1,
-                             base::TimeDelta::FromHours(12).InMinutes(),
-                             50);
-}
-
 }  // anonymous namespace
 
 MetricsReportingScheduler::MetricsReportingScheduler(
@@ -117,7 +109,6 @@ void MetricsReportingScheduler::UploadFinished(bool server_is_healthy,
     upload_interval_ = TimeDelta::FromSeconds(kUnsentLogsIntervalSeconds);
   } else {
     upload_interval_ = GetStandardUploadInterval();
-    last_upload_finish_time_ = base::TimeTicks::Now();
   }
 
   if (running_)
@@ -145,11 +136,6 @@ void MetricsReportingScheduler::TriggerUpload() {
     return;
   }
 
-  if (!last_upload_finish_time_.is_null()) {
-    LogActualUploadInterval(base::TimeTicks::Now() - last_upload_finish_time_);
-    last_upload_finish_time_ = base::TimeTicks();
-  }
-
   callback_pending_ = true;
   upload_callback_.Run();
 }