Histogram for recording actual log upload interval added.

Histogram is in minutes. In case logs are uploaded by multiple tasks the interval between those is not recorded.

BUG=421543

Review URL: https://codereview.chromium.org/633373011

Cr-Commit-Position: refs/heads/master@{#299902}

components/metrics/metrics_reporting_scheduler.cc

@@ -62,6 +62,14 @@ void LogMetricsInitSequence(InitSequence sequence) {
                             INIT_SEQUENCE_ENUM_SIZE);
 }
 
+void LogActualUploadInterval(TimeDelta interval) {
+  UMA_HISTOGRAM_CUSTOM_COUNTS("UMA.ActualLogUploadInterval",
+                             interval.InMinutes(),
+                             1,
+                             base::TimeDelta::FromHours(12).InMinutes(),
+                             50);
+}
+
 // Returns upload interval specified for the current experiment running.
 // TODO(gayane): Only for experimenting with upload interval for Android
 // (bug: 17391128). Should be removed once the experiments are done.
@@ -126,6 +134,7 @@ 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_)
@@ -152,6 +161,12 @@ void MetricsReportingScheduler::TriggerUpload() {
     waiting_for_init_task_complete_ = true;
     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();
 }

components/metrics/metrics_reporting_scheduler.h

@@ -66,6 +66,10 @@ class MetricsReportingScheduler {
   // upload.
   base::TimeDelta upload_interval_;
 
+  // The tick count of the last time log upload has been finished and null if no
+  // upload has been done yet.
+  base::TimeTicks last_upload_finish_time_;
+
   // Indicates that the scheduler is running (i.e., that Start has been called
   // more recently than Stop).
   bool running_;

tools/metrics/histograms/histograms.xml

@@ -35798,6 +35798,14 @@ Therefore, the affected-histogram name has to have at least one dot in it.
   <summary>Whether the scroll is executed on main thread.</summary>
 </histogram>
 
+<histogram name="UMA.ActualLogUploadInterval" units="minutes">
+  <owner>asvitkine@chromium.org</owner>
+  <summary>
+    The actual interval between log upload start and previous log upload
+    finished within the same process.
+  </summary>
+</histogram>
+
 <histogram name="UMA.CleanExitBeaconConsistency" enum="UmaCleanExitConsistency">
   <owner>erikwright@chromium.org</owner>
   <summary>