[es6] Partially implement Reflect.getOwnPropertyDescriptor.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 67a99005cb31aa815d7339fa9f2e457678c9125d..0f017cc77969744f8d53ca0a2db4681132e05a53 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1893,7 +1893,7 @@ class JSReceiver: public HeapObject {
                                         ShouldThrow should_throw);
 
   static bool GetOwnPropertyDescriptor(Isolate* isolate,
-                                       Handle<JSObject> object,
+                                       Handle<JSReceiver> object,
                                        Handle<Object> key,
                                        PropertyDescriptor* desc);
   static bool GetOwnPropertyDescriptor(LookupIterator* it,