chrome/test/data/extensions/api_test/bindings/message_sender/background.js

// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

chrome.test.sendMessage('sender_ready', function(id) {
  chrome.runtime.sendMessage(id, 'from_sender');
});