[es6] Initial steps towards a correct implementation of IsCallable.

src/json.js

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 (function(global, utils) {
 
 "use strict";
 
 %CheckIsBootstrapping();
 
@@ skipping 39 matching lines @@
         }
       }
     }
   }
   return %_CallFunction(holder, name, val, reviver);
 }
 
 
 function JSONParse(text, reviver) {
   var unfiltered = %ParseJson(TO_STRING_INLINE(text));
-  if (IS_SPEC_FUNCTION(reviver)) {
+  if (IS_CALLABLE(reviver)) {
     return Revive({'': unfiltered}, '', reviver);
   } else {
     return unfiltered;
   }
 }
 
 
 function SerializeArray(value, replacer, stack, indent, gap) {
   if (!%PushIfAbsent(stack, value)) throw MakeTypeError(kCircularStructure);
   var stepback = indent;
@@ skipping 67 matching lines @@
   }
   stack.pop();
   return final;
 }
 
 
 function JSONSerialize(key, holder, replacer, stack, indent, gap) {
   var value = holder[key];
   if (IS_SPEC_OBJECT(value)) {
     var toJSON = value.toJSON;
-    if (IS_SPEC_FUNCTION(toJSON)) {
+    if (IS_CALLABLE(toJSON)) {
       value = %_CallFunction(value, key, toJSON);
     }
   }
-  if (IS_SPEC_FUNCTION(replacer)) {
+  if (IS_CALLABLE(replacer)) {
     value = %_CallFunction(holder, key, value, replacer);
   }
   if (IS_STRING(value)) {
     return %QuoteJSONString(value);
   } else if (IS_NUMBER(value)) {
     return JSON_NUMBER_TO_STRING(value);
   } else if (IS_BOOLEAN(value)) {
     return value ? "true" : "false";
   } else if (IS_NULL(value)) {
     return "null";
@@ skipping 85 matching lines @@
 function JsonSerializeAdapter(key, object) {
   var holder = {};
   holder[key] = object;
   // No need to pass the actual holder since there is no replacer function.
   return JSONSerialize(key, holder, UNDEFINED, new InternalArray(), "", "");
 }
 
 %InstallToContext(["json_serialize_adapter", JsonSerializeAdapter]);
 
 })