Optimize JSON stringifying when `replacer` and `space` are falsey.

src/js/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 215 matching lines @@
     space = MaxSimple(0, MinSimple(TO_INTEGER(space), 10));
     gap = %_SubString("          ", 0, space);
   } else if (IS_STRING(space)) {
     if (space.length > 10) {
       gap = %_SubString(space, 0, 10);
     } else {
       gap = space;
     }
   } else {
     gap = "";
   }

[Yang, 2016/02/19 10:36:34]

whitespace before "!gap".

+  if (!IS_CALLABLE(replacer) && !property_list &&!gap && !IS_PROXY(value)) {
+    return %BasicJSONStringify(value);
+  }
   return JSONSerialize('', {'': value}, replacer, new InternalArray(), "", gap);
 }
 
 // -------------------------------------------------------------------
 
 %AddNamedProperty(GlobalJSON, toStringTagSymbol, "JSON", READ_ONLY | DONT_ENUM);
 
 // Set up non-enumerable properties of the JSON object.
 utils.InstallFunctions(GlobalJSON, DONT_ENUM, [
   "parse", JSONParse,
@@ skipping 24 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]);
 
 })