[es6] Object.getPrototypeOf should work with values

test/mjsunit/harmony/set-prototype-of.js

 // Copyright 2014 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 46 matching lines @@
   null
 ];
 
 
 var valuesWithoutNull = coercibleValues.concat(undefined);
 
 
 function TestSetPrototypeOfCoercibleValues() {
   for (var i = 0; i < coercibleValues.length; i++) {
     var value = coercibleValues[i];
-    assertThrows(function() {
-      Object.getPrototypeOf(value);
-    }, TypeError);
-
+    var proto = Object.getPrototypeOf(value);
     assertEquals(Object.setPrototypeOf(value, {}), value);
-
-    assertThrows(function() {
-      Object.getPrototypeOf(value);
-    }, TypeError);
+    assertSame(proto, Object.getPrototypeOf(value));
   }
 }
 TestSetPrototypeOfCoercibleValues();
 
 
 function TestSetPrototypeOfNonCoercibleValues() {
   for (var i = 0; i < nonCoercibleValues.length; i++) {
     var value = nonCoercibleValues[i];
     assertThrows(function() {
       Object.setPrototypeOf(value, {});
@@ skipping 73 matching lines @@
   assertEquals(object.y, 'old y');
 
   var newProto = {
     x: 'new x'
   };
   Object.setPrototypeOf(object, newProto);
   assertEquals(object.x, 'new x');
   assertFalse('y' in object);
 }
 TestLookup();