Set up the infrastructure for Extension event metrics.

chrome/browser/extensions/permissions_updater.cc

Index: chrome/browser/extensions/permissions_updater.cc
diff --git a/chrome/browser/extensions/permissions_updater.cc b/chrome/browser/extensions/permissions_updater.cc
index 9b5530db3a385cfa40293a27c220b9786db2649a..70cbe5bc0d04bbd6344c318c3cbd7da4ef02049b 100644
--- a/chrome/browser/extensions/permissions_updater.cc
+++ b/chrome/browser/extensions/permissions_updater.cc
@@ -340,7 +340,7 @@ void PermissionsUpdater::DispatchEvent(
   scoped_ptr<api::permissions::Permissions> permissions =
       PackPermissionSet(changed_permissions);
   value->Append(permissions->ToValue().release());
-  scoped_ptr<Event> event(new Event(event_name, value.Pass()));
+  scoped_ptr<Event> event(new Event(events::UNKNOWN, event_name, value.Pass()));
   event->restrict_to_browser_context = browser_context_;
   event_router->DispatchEventToExtension(extension_id, event.Pass());
 }