Set up the infrastructure for Extension event metrics.

extensions/browser/api/idle/idle_manager.cc

Index: extensions/browser/api/idle/idle_manager.cc
diff --git a/extensions/browser/api/idle/idle_manager.cc b/extensions/browser/api/idle/idle_manager.cc
index 5e8fc1ad0052ecd524c34660a9cf940db0611d85..a22143656766f052a9b617e3f72b725f20f1e5bb 100644
--- a/extensions/browser/api/idle/idle_manager.cc
+++ b/extensions/browser/api/idle/idle_manager.cc
@@ -49,8 +49,8 @@ void DefaultEventDelegate::OnStateChanged(const std::string& extension_id,
                                           ui::IdleState new_state) {
   scoped_ptr<base::ListValue> args(new base::ListValue());
   args->Append(IdleManager::CreateIdleValue(new_state));
-  scoped_ptr<Event> event(
-      new Event(idle::OnStateChanged::kEventName, args.Pass()));
+  scoped_ptr<Event> event(new Event(
+      events::UNKNOWN, idle::OnStateChanged::kEventName, args.Pass()));
   event->restrict_to_browser_context = context_;
   EventRouter::Get(context_)
       ->DispatchEventToExtension(extension_id, event.Pass());