Implement set trap for proxies, and revamp class hierarchy in preparation

test/mjsunit/json.js

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 364 matching lines @@
 
 var funcJSON = function() { /* Is callable */ };
 funcJSON.toJSON = function() { return "has toJSON"; };
 
 var re = /Is callable/;
 
 var reJSON = /Is callable/;
 reJSON.toJSON = function() { return "has toJSON"; };
 
 assertEquals(
-    '[37,null,1,"foo","37","true",null,"has toJSON",null,"has toJSON"]',
+    '[37,null,1,"foo","37","true",null,"has toJSON",{},"has toJSON"]',
     JSON.stringify([num37, numFoo, numTrue,
                     strFoo, str37, strTrue,
                     func, funcJSON, re, reJSON]));
 
 
 var oddball = Object(42);
 oddball.__proto__ = { __proto__: null, toString: function() { return true; } };
 assertEquals('1', JSON.stringify(oddball));
 
 var getCount = 0;
@@ skipping 26 matching lines @@
 // 
 // Parse a non-object value as __proto__. This must not create a 
 // __proto__ property different from the original, and should not 
 // change the original.
 var o = JSON.parse('{"__proto__":5}');
 assertEquals(Object.prototype, o.__proto__);  // __proto__ isn't changed.
 assertEquals(0, Object.keys(o).length);  // __proto__ isn't added as enumerable.