Fastpath some spread-call desugaring.

src/contexts.h

Index: src/contexts.h
diff --git a/src/contexts.h b/src/contexts.h
index 64f883bb4dd88500e28cb0451dc98aa7a603ddc8..eaaaaa439cf0367b608734431f1ee042fe21549d 100644
--- a/src/contexts.h
+++ b/src/contexts.h
@@ -58,6 +58,7 @@ enum ContextLookupFlags {
   V(REFLECT_DELETE_PROPERTY_INDEX, JSFunction, reflect_delete_property) \
   V(SPREAD_ARGUMENTS_INDEX, JSFunction, spread_arguments)               \
   V(SPREAD_ITERABLE_INDEX, JSFunction, spread_iterable)                 \
+  V(SPREAD_ITERABLE_PREPARE_INDEX, JSFunction, spread_iterable_prepare) \
   V(MATH_FLOOR_INDEX, JSFunction, math_floor)                           \
   V(MATH_POW_INDEX, JSFunction, math_pow)
 
@@ -224,6 +225,7 @@ enum ContextLookupFlags {
   V(GENERATOR_FUNCTION_FUNCTION_INDEX, JSFunction,                             \
     generator_function_function)                                               \
   V(GENERATOR_OBJECT_PROTOTYPE_MAP_INDEX, Map, generator_object_prototype_map) \
+  V(INITIAL_ARRAY_ITERATOR_INDEX, JSObject, initial_array_iterator)            \
   V(INITIAL_ARRAY_PROTOTYPE_INDEX, JSObject, initial_array_prototype)          \
   V(INITIAL_GENERATOR_PROTOTYPE_INDEX, JSObject, initial_generator_prototype)  \
   V(INITIAL_ITERATOR_PROTOTYPE_INDEX, JSObject, initial_iterator_prototype)    \