Add an override flag to enable metrics reporting.

components/metrics_services_manager/metrics_services_manager_client.cc

Index: components/metrics_services_manager/metrics_services_manager_client.cc
diff --git a/components/metrics_services_manager/metrics_services_manager_client.cc b/components/metrics_services_manager/metrics_services_manager_client.cc
new file mode 100644
index 0000000000000000000000000000000000000000..05c68697e121e8ffd024a0c9b42b70182789832b
--- /dev/null
+++ b/components/metrics_services_manager/metrics_services_manager_client.cc
@@ -0,0 +1,13 @@
+// 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_services_manager/metrics_services_manager_client.h"
+
+namespace metrics_services_manager {
+
+bool MetricsServicesManagerClient::IsMetricsReportingForceEnabled() {
+  return false;
+}
+
+}  // namespace metrics_services_manager