Do not cancel request when an error occurs in a webRequest event handler

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

 // Copyright (c) 2011 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.runTests([
   function addListeners() {
     chrome.webRequest.onBeforeRequest.addListener(
         function(details) {}, {urls: ["<all_urls>"]});
     chrome.webRequest.onBeforeSendHeaders.addListener(
         function(details) {}, {urls: ["<all_urls>"]});
@@ skipping 123 matching lines @@
         {types: ["xmlhttprequest"], urls: ["*://*/*"]},
         ["blocking", "responseHeaders"]);
 
     chrome.test.getConfig(function(config) {
       var url = 'http://127.0.0.1:' + config.testServer.port + '/simple.html';
       var xhr = new XMLHttpRequest();
       xhr.open('GET', url);
       xhr.onload = function() {
         chrome.webRequest.onHeadersReceived.removeListener(
             callbackWithBadHeadersResponse);
-
-        chrome.test.fail();
-      };
-      xhr.onerror = function() {
-        chrome.webRequest.onHeadersReceived.removeListener(
-            callbackWithBadHeadersResponse);
-        // When the returned header is invalid, the request should be canceled.
+        var responseHeaders = xhr.getAllResponseHeaders() || '';
+        chrome.test.assertTrue(
+            responseHeaders.indexOf('X-Header-With-Invalid-Value') === -1);
         // TODO(robwu): If possible, check whether an error with the following
         // message has been logged to the JavaScript console:
         // "Header 'X-Header-With-Invalid-Value' has an invalid value"
         chrome.test.succeed();
       };
+      xhr.onerror = function() {
+        chrome.webRequest.onHeadersReceived.removeListener(
+            callbackWithBadHeadersResponse);
+        chrome.test.fail();
+      };
       xhr.send();
     });
   }
 ]);