Fastpath some spread-call desugaring.

src/lookup.h

Index: src/lookup.h
diff --git a/src/lookup.h b/src/lookup.h
index 4e2c69f1e6d499df15bbec35c17ba4ba3129a120..e0b40c40fe21c9650f266baf3cdd10ad9473d656 100644
--- a/src/lookup.h
+++ b/src/lookup.h
@@ -258,7 +258,8 @@ class V8_EXPORT_PRIVATE LookupIterator final BASE_EMBEDDED {
     if (*name_ == heap()->is_concat_spreadable_symbol() ||
         *name_ == heap()->constructor_string() ||
         *name_ == heap()->species_symbol() ||
-        *name_ == heap()->has_instance_symbol()) {
+        *name_ == heap()->has_instance_symbol() ||
+        *name_ == heap()->iterator_symbol()) {

[Yang, 2016/11/14 10:17:19]

If this is a performance concern (which I doubt), we could compare *name_ to
constructor_string first, and then check for IsSymbol before following up with
these symbol compares.

[petermarshall, 2016/11/14 12:52:50]

OK good idea - let's leave it and see if we have any performance issues?

       InternalUpdateProtector();
     }
   }