Check for warnings when loading extensions in browser tests.

chrome/test/data/extensions/api_test/webnavigation/test_userAction.js

 // Copyright (c) 2012 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 runTests() {
+onload = function() {
   var getURL = chrome.extension.getURL;
   chrome.tabs.create({"url": "about:blank"}, function(tab) {
     var tabId = tab.id;
 
     chrome.test.runTests([
       // Opens a tab and waits for the user to click on a link in it.
       function userAction() {
         expect([
           { label: "a-onBeforeNavigate",
             event: "onBeforeNavigate",
@@ skipping 67 matching lines @@
             navigationOrder("b-"),
             [ "a-onDOMContentLoaded",
               "b-onCreatedNavigationTarget",
               "b-onBeforeNavigate" ]]);
 
         // Notify the api test that we're waiting for the user.
         chrome.test.notifyPass();
       },
     ]);
   });
-}
+};