perf: no spread

packages/core/event-emitter.js

@@ -15,7 +15,9 @@ export function EventEmitterMixin(Superclass) {
       this.$$events = Object.create(null);
     }
 
-    addListener(...args) { return this.on(...args); }
+    addListener(typesOrType, fn, that) {
+      return this.on(typesOrType, fn, that);
+    }
 
     // Notify ALL the listeners!
     emit(type, ...args) {