Mark DOMStringList.contains() as deprecated, add console warning.

LayoutTests/storage/indexeddb/mozilla/resources/objectstorenames.js

 // original test:
 // http://mxr.mozilla.org/mozilla2.0/source/dom/indexedDB/test/test_global_data.html
 // license of original test:
 // " Any copyright is dedicated to the Public Domain.
 //   http://creativecommons.org/publicdomain/zero/1.0/ "
 
 if (this.importScripts) {
     importScripts('../../../../resources/js-test.js');
     importScripts('../../resources/shared.js');
 }
 
 description("Test IndexedDB's objectStoreNames array");
 
 indexedDBTest(prepareDatabase);
 function prepareDatabase()
 {
     db = event.target.result;
     event.target.transaction.onabort = unexpectedAbortCallback;
 
     objectStoreName = "a";
     objectStore = evalAndLog("objectStore = db.createObjectStore(objectStoreName, { keyPath: 'id', autoIncrement: true });");
 
     shouldBeTrue("'objectStoreNames' in db");
     shouldBe("db.objectStoreNames.length", "1");
-    shouldBe("db.objectStoreNames.item(0)", "objectStoreName");
+    shouldBe("db.objectStoreNames[0]", "objectStoreName");
     finishJSTest();
 }