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() {
+  base::ThreadRestrictions::ScopedAllowIO allow_io;

[stevenjb, 2014/09/11 20:31:44]

We really shouldn't be using this in production code. We should really pass an
IO thread to this method or to the constructor and use that.

[Alexei Svitkine (slow), 2014/09/11 20:39:43]

Right. Previously we had this statement in metrics_reporting_state.cc which was
also doing IO on UI thread. The code in that file is being fixed by this CL so
that it doesn't do IO on UI thread, but unfortunately this bit of MetricsService
still does (which was previously affected by the other ScopedAllowIO block but
now narrowed down to just this function).

So this ScopedAllowedIO is still needed until we fix the MetricsService code
too, but that should be a separate CL.

[stevenjb, 2014/09/11 20:47:19]

OK, that's fine, but please add a TODO: with the crbug issue# for fixing this,
thanks!

[gayane -on leave until 09-2017, 2014/09/12 17:44:51]

Done.

+
   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