Add histograms for observing UMA throttling effect.

components/metrics/metrics_reporting_scheduler.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_METRICS_METRICS_REPORTING_SCHEDULER_H_
 #define COMPONENTS_METRICS_METRICS_REPORTING_SCHEDULER_H_
 
 #include "base/callback.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
@@ skipping 52 matching lines @@
 
   // The MetricsService method to call when uploading should happen.
   const base::Closure upload_callback_;
 
   base::OneShotTimer upload_timer_;
 
   // The interval between being told an upload is done and starting the next
   // 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_;
 
   // Indicates that the last triggered upload hasn't resolved yet.
   bool callback_pending_;
 
   // Whether the InitTaskComplete() callback has been called.
   bool init_task_complete_;
 
   // Whether the initial scheduled upload timer has fired before the init task
   // has been completed.
   bool waiting_for_init_task_complete_;
 
   // Callback function used to get the standard upload time.
   base::Callback<base::TimeDelta(void)> upload_interval_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsReportingScheduler);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_METRICS_REPORTING_SCHEDULER_H_