Fastpath some spread-call desugaring.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 22888fc7f2e90e1b07a380208a79a27689402bc7..24bc0c9756cbc1f968999f64f217cefb1a4561f0 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -985,8 +985,8 @@ class Isolate {
 
   Map* get_initial_js_array_map(ElementsKind kind);
 
-  static const int kArrayProtectorValid = 1;
-  static const int kArrayProtectorInvalid = 0;
+  static const int kProtectorValid = 1;
+  static const int kProtectorInvalid = 0;
 
   bool IsFastArrayConstructorPrototypeChainIntact();
   inline bool IsArraySpeciesLookupChainIntact();
@@ -994,6 +994,7 @@ class Isolate {
   bool IsIsConcatSpreadableLookupChainIntact();
   bool IsIsConcatSpreadableLookupChainIntact(JSReceiver* receiver);
   inline bool IsStringLengthOverflowIntact();
+  inline bool IsArrayIteratorLookupChainIntact();
 
   // On intent to set an element in object, make sure that appropriate
   // notifications occur if the set is on the elements of the array or
@@ -1013,6 +1014,7 @@ class Isolate {
   void InvalidateHasInstanceProtector();
   void InvalidateIsConcatSpreadableProtector();
   void InvalidateStringLengthOverflowProtector();
+  void InvalidateArrayIteratorProtector();
 
   // Returns true if array is the initial array prototype in any native context.
   bool IsAnyInitialArrayPrototype(Handle<JSArray> array);