Add test that inherited properties are preserved for synthetic change records

test/mjsunit/es7/object-observe.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 192 matching lines @@
   type: 'delete',
   name: 'bar',
   expando2: 'str'
 });
 Object.deliverChangeRecords(observer.callback);
 observer.assertCallbackRecords([
   { object: obj, name: 'foo', type: 'update', expando: 1 },
   { object: obj, name: 'bar', type: 'delete', expando2: 'str' }
 ]);
 
+// Properties from prototype of synthetic change records are preserved
+reset();
+Object.observe(obj, observer.callback);
+notifier = Object.getNotifier(obj);
+var proto = {
+  type: 'update',
+  foo: 'bar'
+};
+var rec = Object.create(proto);
+rec.oldValue = 3;
+notifier.notify(rec);
+
+proto.type = 'delete';
+rec.oldValue = 5;
+
+notifier.performChange('delete', function() {
+  return rec;
+});
+
+Object.deliverChangeRecords(observer.callback);
+observer.assertCallbackRecords([
+  { object: obj, type: 'update', foo: 'bar', oldValue: 3 },
+  { object: obj, type: 'delete', foo: 'bar', oldValue: 5 },
+]);
+
 // Non-string accept values are coerced to strings
 reset();
 Object.observe(obj, observer.callback, [true, 1, null, undefined]);
 notifier = Object.getNotifier(obj);
 notifier.notify({ type: 'true' });
 notifier.notify({ type: 'false' });
 notifier.notify({ type: '1' });
 notifier.notify({ type: '-1' });
 notifier.notify({ type: 'null' });
 notifier.notify({ type: 'nill' });
@@ skipping 1566 matching lines @@
     for (var n1 = 0; n1 < 3; ++n1)
       for (var n2 = 0; n2 < 3; ++n2)
         for (var i in mutation)
           TestFastElementsLength(mutation[i], b1 != 0, b2 != 0, 20*n1, 20*n2);
 
 for (var b1 = 0; b1 < 2; ++b1)
   for (var b2 = 0; b2 < 2; ++b2)
     for (var n = 0; n < 3; ++n)
       for (var i in mutationByIncr)
         TestFastElementsLength(mutationByIncr[i], b1 != 0, b2 != 0, 7*n, 7*n+1);