Update ObjectToString to Harmony-draft algorithm

test/mjsunit/es6/collections.js

 // Copyright 2012 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 282 matching lines @@
 assertEquals("Set", Set.name);
 assertEquals("Map", Map.name);
 assertEquals("WeakMap", WeakMap.name);
 assertEquals("WeakSet", WeakSet.name);
 
 
 // Test prototype property of Set, Map, WeakMap and WeakSet.
 function TestPrototype(C) {
   assertTrue(C.prototype instanceof Object);
   assertEquals({
-    value: {},
+    value: C.prototype,
     writable: false,
     enumerable: false,
     configurable: false
   }, Object.getOwnPropertyDescriptor(C, "prototype"));
 }
 TestPrototype(Set);
 TestPrototype(Map);
 TestPrototype(WeakMap);
 TestPrototype(WeakSet);
 
@@ skipping 1045 matching lines @@
 
   var map = new ctor(42);
   assertSize(2, map);
   assertEquals(1, map.get(k1));
   assertEquals(2, map.get(k2));
 
   delete Number.prototype[Symbol.iterator];
 }
 TestMapConstructorIterableValue(Map);
 TestMapConstructorIterableValue(WeakMap);
+
+function TestCollectionToString(C) {
+  assertEquals("[object " + C.name + "]",
+      Object.prototype.toString.call(new C()));
+}
+TestCollectionToString(Map);
+TestCollectionToString(Set);
+TestCollectionToString(WeakMap);
+TestCollectionToString(WeakSet);