Add an override flag to enable metrics reporting.

components/metrics_services_manager/metrics_services_manager.cc

Index: components/metrics_services_manager/metrics_services_manager.cc
diff --git a/components/metrics_services_manager/metrics_services_manager.cc b/components/metrics_services_manager/metrics_services_manager.cc
index 5987635fbacfbf3d479b89ff07eeb33c4e116827..61d41327775c3c071538636354b3f45c9c012d32 100644
--- a/components/metrics_services_manager/metrics_services_manager.cc
+++ b/components/metrics_services_manager/metrics_services_manager.cc
@@ -132,6 +132,7 @@ void MetricsServicesManager::UpdateUkmService() {
   if (!ukm)
     return;
   bool sync_enabled =
+      client_->IsMetricsReportingEnabledForTesting() ||
       metrics_service_client_->IsHistorySyncEnabledOnAllProfiles();
   if (may_record_ && sync_enabled) {
     ukm->EnableRecording();
@@ -146,7 +147,10 @@ void MetricsServicesManager::UpdateUkmService() {
 }
 
 void MetricsServicesManager::UpdateUploadPermissions(bool may_upload) {
-  UpdatePermissions(client_->IsMetricsReportingEnabled(), may_upload);
+  UpdatePermissions(
+      (client_->IsMetricsReportingEnabledForTesting() ||
+       client_->IsMetricsReportingEnabled()),
+      client_->IsMetricsReportingEnabledForTesting() || may_upload);
 }
 
 }  // namespace metrics_services_manager