Define EnabledComponentUpdates group policy for the component updater.

chrome/browser/plugins/plugin_observer.cc

Index: chrome/browser/plugins/plugin_observer.cc
diff --git a/chrome/browser/plugins/plugin_observer.cc b/chrome/browser/plugins/plugin_observer.cc
index 2494c3843cf9c1982eaf6ff91c937f4bd6f07eaa..44aac14c052575da14b8c02c8b0449ec5d0f1dd3 100644
--- a/chrome/browser/plugins/plugin_observer.cc
+++ b/chrome/browser/plugins/plugin_observer.cc
@@ -417,7 +417,8 @@ void PluginObserver::OnBlockedComponentUpdatedPlugin(
   component_observers_[placeholder_id] =
       base::MakeUnique<ComponentObserver>(this, placeholder_id, identifier);
   g_browser_process->component_updater()->GetOnDemandUpdater().OnDemandUpdate(
-      identifier);
+      identifier,
+      component_updater::ComponentUpdateService::CompletionCallback());
 }
 
 void PluginObserver::RemoveComponentObserver(int placeholder_id) {