Check for warnings when loading extensions in browser tests.

chrome/test/data/extensions/api_test/webnavigation/test_iframe.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([
       // Navigates to a.html which includes b.html as an iframe. b.html
       // redirects to c.html.
       function iframe() {
         expect([
           { label: "a-onBeforeNavigate",
@@ skipping 326 matching lines @@
                        url: getURL('iframe/c.html') }}],
           [ navigationOrder("h-"),
             navigationOrder("i-"),
             navigationOrder("c-"),
             isIFrameOf("i-", "h-"),
             isLoadedBy("c-", "i-") ]);
         chrome.tabs.update(tabId, { url: getURL('iframe/h.html') });
       },
     ]);
   });
-}
+};