Improve implementation of isInstanceOf in JSONSchemaValidator.

chrome/renderer/resources/extensions/json_schema.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.
 
 // -----------------------------------------------------------------------------
 // NOTE: If you change this file you need to touch renderer_resources.grd to
 // have your change take effect.
 // -----------------------------------------------------------------------------
 
 //==============================================================================
@@ skipping 262 matching lines @@
         this.validate(instance[prop], schema.properties[prop], propPath);
       } else if (!schema.properties[prop].optional) {
         this.addError(propPath, "propertyRequired");
       }
     }
   }
 
   // If "instanceof" property is set, check that this object inherits from
   // the specified constructor (function).
   if (schema.isInstanceOf) {
-    var isInstance = function() {
-      var constructor = this[schema.isInstanceOf];
-      if (constructor) {
-        return (instance instanceof constructor);
-      }
-
-      // Special-case constructors that can not always be found on the global
-      // object, but for which we to allow validation.
-      var allowedNamedConstructors = {
-        "Window": true,
-        "ImageData": true
-      }
-      if (!allowedNamedConstructors[schema.isInstanceOf]) {
-        throw "Attempt to validate against an instance ctor that could not be" +
-              "found: " + schema.isInstanceOf;
-      }
-      return (schema.isInstanceOf == instance.constructor.name)
-    }();
-
-    if (!isInstance)
+    if (Object.prototype.toString.call(instance) !=

[arv (Not doing code reviews), 2012/03/02 19:58:28]

It seems a bit cleaner to get the substring here

Object.prototype.toString.call(instance).slice(8, -1) != schema.isInstanceOf

[Aaron Boodman, 2012/03/02 22:54:26]

Disagree. I think the intention of the code is much clearer the way it is than
what you propose, and I dislike the magic number.

+        "[object " + schema.isInstanceOf + "]") {
       this.addError(propPath, "notInstance", [schema.isInstanceOf]);
+    }
   }
 
   // Exit early from additional property check if "type":"any" is defined.
   if (schema.additionalProperties &&
       schema.additionalProperties.type &&
       schema.additionalProperties.type == "any") {
     return;
   }
 
   // By default, additional properties are not allowed on instance objects. This
@@ skipping 130 matching lines @@
  */
 chromeHidden.JSONSchemaValidator.prototype.addError = function(
     path, key, replacements) {
   this.errors.push({
     path: path,
     message: chromeHidden.JSONSchemaValidator.formatError(key, replacements)
   });
 };
 
 })();