Disable sending persistent histograms from last session by default.

components/metrics/file_metrics_provider.cc

 // Copyright 2016 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.
 
 #include "components/metrics/file_metrics_provider.h"
 
 #include "base/command_line.h"
 #include "base/files/file.h"
 #include "base/files/file_enumerator.h"
 #include "base/files/file_util.h"
@@ skipping 473 matching lines @@
   // will continue to be used by the caller after that method returns. Once
   // here, though, all actions to be done on the data have been completed.
   for (const std::unique_ptr<SourceInfo>& source : sources_for_previous_run_)
     DeleteFileAsync(source->path);
   sources_for_previous_run_.clear();
 }
 
 bool FileMetricsProvider::HasInitialStabilityMetrics() {
   DCHECK(thread_checker_.CalledOnValidThread());
 
-  // Check if there is an experiment that disables stability metrics.
-  std::string unreported = variations::GetVariationParamValueByFeature(
-      base::kPersistentHistogramsFeature, "send_unreported_metrics");
-  if (unreported == "no")
-    sources_for_previous_run_.clear();
-
   // Measure the total time spent checking all sources as well as the time
   // per individual file. This method is called during startup and thus blocks
   // the initial showing of the browser window so it's important to know the
   // total delay.
   SCOPED_UMA_HISTOGRAM_TIMER("UMA.FileMetricsProvider.InitialCheckTime.Total");
 
   // Check all sources for previous run to see if they need to be read.
   for (auto iter = sources_for_previous_run_.begin();
        iter != sources_for_previous_run_.end();) {
     SCOPED_UMA_HISTOGRAM_TIMER("UMA.FileMetricsProvider.InitialCheckTime.File");
@@ skipping 60 matching lines @@
   // important to know how much total "jank" may be introduced.
   SCOPED_UMA_HISTOGRAM_TIMER("UMA.FileMetricsProvider.SnapshotTime.Total");
 
   for (std::unique_ptr<SourceInfo>& source : sources_mapped_) {
     SCOPED_UMA_HISTOGRAM_TIMER("UMA.FileMetricsProvider.SnapshotTime.File");
     MergeHistogramDeltasFromSource(source.get());
   }
 }
 
 }  // namespace metrics