[es6] Make sure we call add property when adding a new property

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index 180eb63536c1f35bf5d07189478a81c55951d281..fad3d2e0264420b272408a91f9b71bbade6df13a 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -3333,7 +3333,8 @@ MaybeHandle<Object> Object::SetSuperProperty(LookupIterator* it,
       MaybeHandle<Object> result = SetPropertyInternal(
           &own_lookup, value, language_mode, store_mode, &found);
       if (found) return result;
-      return SetDataProperty(&own_lookup, value);
+      return AddDataProperty(&own_lookup, value, NONE, language_mode,

[arv (Not doing code reviews), 2015/06/01 14:17:58]

AddDataProperty has a DCHECK that the receiver is not a proxy.

Can found be false afte a proxy trap is invoked?

[caitp (gmail), 2015/06/01 14:36:38]

In the current implementation, found can be false if the property key is a
Symbol (the proxy trap is never invoked in this case).

[Toon Verwaest, 2015/06/01 14:37:03]

Not if the receiver is the proxy, as is the case here.

[Toon Verwaest, 2015/06/01 14:41:29]

I think you'd want to make this switch nested in a for-loop like is the case for
other Set with iterator. After ruling out the interceptor / access check, you
just continue with whatever is behind the interceptor / access check. Behind the
access check could be an interceptor. Behind the interceptor could be data, or
not-found.

+                             store_mode);
     }
   }