Attend to review comments

Author: brizental

benchmarks/size/core.js

@@ -1,3 +1,7 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
 // Metrics
 import BooleanMetricType from "@mozilla/glean/private/metrics/boolean";
 import CounterMetricType from "@mozilla/glean/private/metrics/counter";