Decouple Metrics Initialization from IO Thread Initialization

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 518 matching lines @@
   local_state_->SetInteger(prefs::kStabilityDeferredCount, 0);
   // Note: kStabilityDiscardCount is not cleared as its intent is to measure
   // the number of times data is discarded, even across versions.
   local_state_->SetInteger(prefs::kStabilityVersionMismatchCount, 0);
 }
 
 void MetricsService::PushExternalLog(const std::string& log) {
   log_manager_.StoreLog(log, MetricsLog::ONGOING_LOG);
 }
 
-UpdateUsagePrefCallbackType MetricsService::GetDataUseForwardingCallback() {
+void MetricsService::UpdateMetricsUsagePrefs(const std::string& service_name,
+                                             int message_size,
+                                             bool is_cellular) {
   DCHECK(IsSingleThreaded());
-
   if (data_use_tracker_) {
-    return data_use_tracker_->GetDataUseForwardingCallback(
-        base::ThreadTaskRunnerHandle::Get());
+    data_use_tracker_->UpdateMetricsUsagePrefs(service_name,
+                                               message_size,
+                                               is_cellular);
   }
-  return UpdateUsagePrefCallbackType();
 }
 
 void MetricsService::MergeHistogramDeltas() {
   for (MetricsProvider* provider : metrics_providers_)
     provider->MergeHistogramDeltas();
 }
 
 //------------------------------------------------------------------------------
 // private methods
 //------------------------------------------------------------------------------
@@ skipping 669 matching lines @@
                  base::Time::Now().ToTimeT());
 }
 
 void MetricsService::SkipAndDiscardUpload() {
   log_manager_.DiscardStagedLog();
   scheduler_->UploadCancelled();
   log_upload_in_progress_ = false;
 }
 
 }  // namespace metrics