[Extensions Bindings] Return result from event dispatch

chrome/test/data/extensions/api_test/native_bindings/extension/content_script.js

Index: chrome/test/data/extensions/api_test/native_bindings/extension/content_script.js
diff --git a/chrome/test/data/extensions/api_test/native_bindings/extension/content_script.js b/chrome/test/data/extensions/api_test/native_bindings/extension/content_script.js
index b837db3abb141fd75d01caf83b2993ec8f099526..1a0d5407d26329fea9d37af8f3bbcdba87e99cb4 100644
--- a/chrome/test/data/extensions/api_test/native_bindings/extension/content_script.js
+++ b/chrome/test/data/extensions/api_test/native_bindings/extension/content_script.js
@@ -2,11 +2,23 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-chrome.runtime.onConnect.addListener((port) => {
+chrome.runtime.onConnect.addListener(function listener(port) {
   port.onMessage.addListener((message) => {
     chrome.test.assertEq('background page', message);
     port.postMessage('content script');
   });
+  chrome.runtime.onConnect.removeListener(listener);
+});
+
+chrome.runtime.onMessage.addListener(
+    function listener(message, sender, sendResponse) {
+  chrome.test.assertEq('async bounce', message);
+  chrome.runtime.onMessage.removeListener(listener);
+  // Respond asynchronously.
+  setTimeout(() => { sendResponse('bounced'); }, 0);
+  // When returning a result asynchronously, the listener must return true -
+  // otherwise the channel is immediately closed.
+  return true;
 });
 
 chrome.runtime.sendMessage('startFlow', function(response) {