Add an override flag to enable metrics reporting.

components/metrics_services_manager/metrics_services_manager_client.h

Index: components/metrics_services_manager/metrics_services_manager_client.h
diff --git a/components/metrics_services_manager/metrics_services_manager_client.h b/components/metrics_services_manager/metrics_services_manager_client.h
index 1490ff984f857fe366d5683d18e9ffcbbf964f62..1915739f3f2204f55880260a4caddb87eb84254c 100644
--- a/components/metrics_services_manager/metrics_services_manager_client.h
+++ b/components/metrics_services_manager/metrics_services_manager_client.h
@@ -57,6 +57,9 @@ class MetricsServicesManagerClient {
   // Update the running state of metrics services managed by the embedder, for
   // example, crash reporting.
   virtual void UpdateRunningServices(bool may_record, bool may_upload) {}
+
+  // If the user has forced metrics collection on via the override flag.
+  virtual bool IsMetricsReportingEnabledForTesting();
 };
 
 }  // namespace metrics_services_manager