Fastpath some spread-call desugaring.

src/parsing/parser.cc

Index: src/parsing/parser.cc
diff --git a/src/parsing/parser.cc b/src/parsing/parser.cc
index 2694722d341396bfb75af5c608d97dd6871567e3..429d625d6a0e38590328487f989b31f4e3bff66c 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -3961,7 +3961,7 @@ ZoneList<Expression*>* Parser::PrepareSpreadArguments(
     ZoneList<Expression*>* spread_list =
         new (zone()) ZoneList<Expression*>(0, zone());
     spread_list->Add(list->at(0)->AsSpread()->expression(), zone());
-    args->Add(factory()->NewCallRuntime(Context::SPREAD_ITERABLE_INDEX,
+    args->Add(factory()->NewCallRuntime(Context::SPREAD_ITERABLE_PREPARE_INDEX,
                                         spread_list, kNoSourcePosition),
               zone());
     return args;