Consolidates accessing and setting the UMA pref to be within metrics code

components/metrics/metrics_state_manager.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.
 
 #include "components/metrics/metrics_state_manager.h"
 
 #include "base/command_line.h"
 #include "base/guid.h"
 #include "base/metrics/histogram.h"
 #include "base/metrics/sparse_histogram.h"
 #include "base/prefs/pref_registry_simple.h"
 #include "base/prefs/pref_service.h"
 #include "base/rand_util.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/threading/thread_restrictions.h"
 #include "base/time/time.h"
 #include "components/metrics/cloned_install_detector.h"
 #include "components/metrics/machine_id_provider.h"
 #include "components/metrics/metrics_pref_names.h"
 #include "components/metrics/metrics_switches.h"
 #include "components/variations/caching_permuted_entropy_provider.h"
 
 namespace metrics {
 
 namespace {
@@ skipping 186 matching lines @@
   ClonedInstallDetector::RegisterPrefs(registry);
   CachingPermutedEntropyProvider::RegisterPrefs(registry);
 
   // TODO(asvitkine): Remove these once a couple of releases have passed.
   // http://crbug.com/357704
   registry->RegisterStringPref(prefs::kMetricsOldClientID, std::string());
   registry->RegisterIntegerPref(prefs::kMetricsOldLowEntropySource, 0);
 }
 
 void MetricsStateManager::BackUpCurrentClientInfo() {
+  // TODO(gayane): Eliminate use of ScopedAllowIO. crbug.com/413783
+  base::ThreadRestrictions::ScopedAllowIO allow_io;
+
   ClientInfo client_info;
   client_info.client_id = client_id_;
   client_info.installation_date = local_state_->GetInt64(prefs::kInstallDate);
   client_info.reporting_enabled_date =
       local_state_->GetInt64(prefs::kMetricsReportingEnabledTimestamp);
   store_client_info_.Run(client_info);
 }
 
 scoped_ptr<ClientInfo> MetricsStateManager::LoadClientInfoAndMaybeMigrate() {
   scoped_ptr<metrics::ClientInfo> client_info = load_client_info_.Run();
@@ skipping 71 matching lines @@
 
   local_state_->ClearPref(prefs::kMetricsClientID);
   local_state_->ClearPref(prefs::kMetricsLowEntropySource);
   local_state_->ClearPref(prefs::kMetricsResetIds);
 
   // Also clear the backed up client info.
   store_client_info_.Run(ClientInfo());
 }
 
 }  // namespace metrics