[Metrics] Make MetricsStateManager take a callback param to check if UMA is enabled.

chrome/browser/metrics/metrics_services_manager.h

Index: chrome/browser/metrics/metrics_services_manager.h
diff --git a/chrome/browser/metrics/metrics_services_manager.h b/chrome/browser/metrics/metrics_services_manager.h
index 66d0c2a8fae36d829a9b76c83d5bcb23c195e230..dadf29ec982a8a1809df2da0f5995823631cd688 100644
--- a/chrome/browser/metrics/metrics_services_manager.h
+++ b/chrome/browser/metrics/metrics_services_manager.h
@@ -45,6 +45,9 @@ class MetricsServicesManager {
  private:
   metrics::MetricsStateManager* GetMetricsStateManager();
 
+  // Returns true iff metrics reporting is enabled.
+  bool IsMetricsReportingEnabled() const;
+
   // Ensures that all functions are called from the same thread.
   base::ThreadChecker thread_checker_;