Support experiment configurations with/without stability metrics.

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"
 #include "base/files/memory_mapped_file.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_base.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/persistent_histogram_allocator.h"
 #include "base/metrics/persistent_memory_allocator.h"
 #include "base/strings/string_piece.h"
 #include "base/task_runner.h"
 #include "base/time/time.h"
 #include "components/metrics/metrics_pref_names.h"
 #include "components/metrics/metrics_service.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
+#include "components/variations/variations_associated_data.h"
 
 namespace metrics {
 
 namespace {
 
 // These structures provide values used to define how files are opened and
 // accessed. It obviates the need for multiple code-paths within several of
 // the methods.
 struct SourceOptions {
   // The flags to be used to open a file on disk.
@@ skipping 429 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 @@
 
     // Dump all histograms contained within the source to the snapshot-manager.
     RecordHistogramSnapshotsFromSource(snapshot_manager, source.get());
 
     // Update the last-seen time so it isn't read again unless it changes.
     RecordSourceAsRead(source.get());
   }
 }
 
 }  // namespace metrics