Move object literal checking into checker classes

test/mjsunit/object-literal-multiple-proto-fields.js

 // Copyright 2015 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.
 
 var p1 = {};
 var p2 = {};
 var p3 = {};
 var x = 0;
-var y = 0;
-var z = 0;
-var o = {
-  __proto__: (x++, p1),
-  __proto__: (y++, p2),
-  __proto__: (z++, p3)
-};
-assertEquals(1, x);
+var y = 1;
+var z = 2;
+var o = 3;
+assertThrows(
+    'o = {' +
+    '  __proto__: (x++, p1),' +
+    '  __proto__: (y++, p2),' +
+    '  __proto__: (z++, p3)' +
+    '};', SyntaxError);
+assertEquals(0, x);
 assertEquals(1, y);
-assertEquals(1, z);
-assertEquals(Object.getPrototypeOf(o), p3);
+assertEquals(2, z);
+assertEquals(3, o);