[extension bindings] Remove leak of internal class

extensions/renderer/resources/utils.js

 // 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.
 
 var nativeDeepCopy = requireNative('utils').deepCopy;
 var schemaRegistry = requireNative('schema_registry');
 var CHECK = requireNative('logging').CHECK;
 var DCHECK = requireNative('logging').DCHECK;
 var WARNING = requireNative('logging').WARNING;
 
@@ skipping 89 matching lines @@
  *          functions: ?Array<string>,
  *          properties: ?Array<string>,
  *          readonly: ?Array<string>}} exposed The names of properties on the
  *     implementation class to be exposed. |superclass| represents the
  *     constructor of the class to be used as the superclass of the exposed
  *     class; |functions| represents the names of functions which should be
  *     delegated to the implementation; |properties| are gettable/settable
  *     properties and |readonly| are read-only properties.
  */
 function expose(publicClass, privateClass, exposed) {
-  DCHECK(!(privateClass.prototype instanceof $Object.self));
-
   $Object.setPrototypeOf(exposed, null);
 
   // This should be called by publicClass.
   privates(publicClass).constructPrivate = function(self, args) {
     if (!(self instanceof publicClass)) {
       throw new Error('Please use "new ' + publicClass.name + '"');
     }
     // The "instanceof publicClass" check can easily be spoofed, so we check
     // whether the private impl is already set before continuing.
     var privateSelf = privates(self);
@@ skipping 109 matching lines @@
   });
 }
 
 exports.$set('forEach', forEach);
 exports.$set('loadTypeSchema', loadTypeSchema);
 exports.$set('lookup', lookup);
 exports.$set('defineProperty', defineProperty);
 exports.$set('expose', expose);
 exports.$set('deepCopy', deepCopy);
 exports.$set('promise', promise);