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 f283b13b989689fc428c2b99d27006433d56cc87..9e7f3ad38eac62ad77a9d6a398e94fc24452be11 100644
--- a/src/parsing/parser.cc
+++ b/src/parsing/parser.cc
@@ -3973,7 +3973,7 @@ 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(Runtime::kSpreadIterablePrepare,
                                         spread_list, kNoSourcePosition),
               zone());
     return args;