Add histograms for observing UMA throttling effect.

components/metrics/metrics_service.cc

 // 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.
 
 //------------------------------------------------------------------------------
 // Description of the life cycle of a instance of MetricsService.
 //
 //  OVERVIEW
 //
 // A MetricsService instance is typically created at application startup.  It is
@@ skipping 868 matching lines @@
   }
   if (!log_manager_.has_staged_log())
     log_manager_.StageNextLogForUpload();
 
   // Proceed to stage the log for upload if log size satisfies cellular log
   // upload constrains.
   if (client_->IsUMACellularUploadLogicEnabled() &&
       !data_use_tracker_->ShouldUploadLogOnCellular(
           log_manager_.staged_log_hash().size())) {
     scheduler_->UploadCancelled();
+    UMA_HISTOGRAM_COUNTS("UMA.LogUpload.Canceled.CellularConstraint", 1);

[Alexei Svitkine (slow), 2016/04/08 15:08:32]

UMA_HISTOGRAM_COUNTS() allocated 50 buckets. You can use
UMA_HISTOGRAM_BOOLEAN(..., true); to log the same data more efficiently.

I suggest logging both the true and false cases, so we can get a ratio.

[gayane -on leave until 09-2017, 2016/04/08 17:19:25]

I have added the false case here, but it wouldn't mean that the log will
certainly get uploaded.

   } else {
     SendStagedLog();
   }
 }
 
 bool MetricsService::ProvidersHaveInitialStabilityMetrics() {
   // Check whether any metrics provider has initial stability metrics.
   for (MetricsProvider* provider : metrics_providers_) {
     if (provider->HasInitialStabilityMetrics())
       return true;
@@ skipping 284 matching lines @@
                  base::Time::Now().ToTimeT());
 }
 
 void MetricsService::SkipAndDiscardUpload() {
   log_manager_.DiscardStagedLog();
   scheduler_->UploadCancelled();
   log_upload_in_progress_ = false;
 }
 
 }  // namespace metrics