Support WebSocket in WebRequest API.

chrome/test/data/extensions/api_test/webrequest/websocket.js

+// Copyright 2017 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.
+
+function getWSTestURL(port) {
+  return 'ws://localhost:' + port + '/echo-with-no-extension';
+}
+
+// Tries to: open a WebSocket, write a test message to it, close it. Verifies
+// that all the necessary events are triggered if |expectedToConnect|, otherwise
+// makes sure WebSocket terminates with an error.
+function testWebSocketConnection(url, expectedToConnect) {
+  var ws = new WebSocket(url);
+  var kMessage = 'test message';
+
+  var keepAlive = chrome.test.callbackAdded();
+
+  ws.onerror = function(error) {
+    chrome.test.log('WebSocket error: ' + error);
+    chrome.test.assertFalse(expectedToConnect);
+    keepAlive();
+  };
+  ws.onmessage = function(messageEvent) {
+    chrome.test.log('Message received: ' + messageEvent.data);
+    chrome.test.assertTrue(expectedToConnect);
+    chrome.test.assertEq(kMessage, messageEvent.data);
+    ws.close();
+  };
+  ws.onclose = function(event) {
+    chrome.test.log('WebSocket closed.');
+    chrome.test.assertEq(expectedToConnect, event.wasClean);
+  }
+
+  ws.onopen = function() {
+    chrome.test.log('WebSocket opened.');
+    chrome.test.assertTrue(expectedToConnect);
+    keepAlive();
+    ws.send(kMessage);
+  };
+}