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

LayoutTests/storage/indexeddb/mozilla/resources/global-data.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');
 }
@@ skipping 13 matching lines @@
     request.onsuccess = open2Success;
     request.onerror = unexpectedErrorCallback;
 }
 
 function open2Success()
 {
     db2 = evalAndLog("db2 = event.target.result");
 
     shouldBeTrue("db1 !== db2");
     shouldBe("db1.objectStoreNames.length", "1");
-    shouldBe("db1.objectStoreNames.item(0)", "objectStoreName");
+    shouldBe("db1.objectStoreNames[0]", "objectStoreName");
     shouldBe("db2.objectStoreNames.length", "1");
-    shouldBe("db2.objectStoreNames.item(0)", "objectStoreName");
+    shouldBe("db2.objectStoreNames[0]", "objectStoreName");
 
     objectStore1 = evalAndLog("objectStore1 = db1.transaction(objectStoreName).objectStore(objectStoreName);");
     shouldBe("objectStore1.name", "objectStoreName");
     shouldBe("objectStore1.keyPath", "objectStoreOptions.keyPath");
 
     objectStore2 = evalAndLog("objectStore2 = db2.transaction(objectStoreName).objectStore(objectStoreName);");
     shouldBeTrue("objectStore1 !== objectStore2");
     shouldBe("objectStore2.name", "objectStoreName");
     shouldBe("objectStore2.keyPath", "objectStoreOptions.keyPath");
 
     finishJSTest();
 }