Add test that inherited properties are preserved for synthetic change records

test/mjsunit/es7/object-observe.js

Index: test/mjsunit/es7/object-observe.js
diff --git a/test/mjsunit/es7/object-observe.js b/test/mjsunit/es7/object-observe.js
index 20a2d160514ee554a9a091512d309a43a9ccd32a..923774dc7d26b2e100dea0c6b99206a42c1a42ec 100644
--- a/test/mjsunit/es7/object-observe.js
+++ b/test/mjsunit/es7/object-observe.js
@@ -210,6 +210,31 @@ observer.assertCallbackRecords([
   { 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]);