Implement externally_connectable! Web pages can now communicate directly with

chrome/test/data/extensions/api_test/messaging/externally_connectable/web_connectable/background.js

+// Copyright 2013 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.
+
+// The test extension for externally_connectable just echos all messages it
+// gets. The test runners are in the sites/ directory.
+
+chrome.runtime.onMessageExternal.addListener(function(message, sender, reply) {
+  reply({ message: message, sender: sender });
+});
+
+chrome.runtime.onConnectExternal.addListener(function(port) {
+  port.onMessage.addListener(function(message) {
+    port.postMessage({ message: message, sender: port.sender });
+  });
+});