Revert of Make DOMWrapperWorld::current() return a reference instead of a pointer

Source/bindings/tests/idls/TestSpecialOperationsInt.idl

+// Copyright 2014 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.
+
+interface TestSpecialOperationsInt {
+    getter long (unsigned long index);
+    setter void (unsigned long index, unsigned long value);
+
+    getter long (DOMString name);
+    setter void (DOMString name, unsigned long value);
+};