Add test case for issue 2793 about experimental natives.

test/mjsunit/harmony/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 270 matching lines @@
 assertEquals("Object", %_ClassOf(WeakMap.prototype))
 
 
 // Test name of constructor.
 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: {},
+    writable: true,  // TODO(2793): This should be non-writable.
+    enumerable: false,
+    configurable: false
+  }, Object.getOwnPropertyDescriptor(C, "prototype"));
+}
+TestPrototype(Set);
+TestPrototype(Map);
+TestPrototype(WeakMap);
+TestPrototype(WeakSet);
+
+
 // Test constructor property of the Set, Map, WeakMap and WeakSet prototype.
 function TestConstructor(C) {
   assertFalse(C === Object.prototype.constructor);
   assertSame(C, C.prototype.constructor);
   assertSame(C, C().__proto__.constructor);
   assertSame(C, (new C).__proto__.constructor);
 }
 TestConstructor(Set);
 TestConstructor(Map);
 TestConstructor(WeakMap);
 TestConstructor(WeakSet);
 
 
+// Test the Set, Map, WeakMap and WeakSet global properties themselves.
 function TestDescriptor(global, C) {
   assertEquals({
     value: C,
     writable: true,
     enumerable: false,
     configurable: true
   }, Object.getOwnPropertyDescriptor(global, C.name));
 }
 TestDescriptor(this, Set);
 TestDescriptor(this, Map);
@@ skipping 147 matching lines @@
 
 // Test WeakSet clear
 (function() {
   var k = new Object();
   var w = new WeakSet();
   w.add(k);
   assertTrue(w.has(k));
   w.clear();
   assertFalse(w.has(k));
 })();