Add an override flag to enable metrics reporting.

chrome/browser/metrics/chrome_metrics_services_manager_client.cc

 // Copyright 2015 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 "chrome/browser/metrics/chrome_metrics_services_manager_client.h"
 
 #include "base/command_line.h"
 #include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 273 matching lines @@
 ChromeMetricsServicesManagerClient::GetMetricsStateManager() {
   DCHECK(thread_checker_.CalledOnValidThread());
   if (!metrics_state_manager_) {
     metrics_state_manager_ = metrics::MetricsStateManager::Create(
         local_state_, enabled_state_provider_.get(),
         base::Bind(&PostStoreMetricsClientInfo),
         base::Bind(&GoogleUpdateSettings::LoadMetricsClientInfo));
   }
   return metrics_state_manager_.get();
 }
+
+bool ChromeMetricsServicesManagerClient::IsMetricsReportingEnabledForTesting() {
+  return ChromeMetricsServiceClient::IsMetricsReportingEnabledForTesting();
+}