Fastpath some spread-call desugaring.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index 157c3f90215b27b6a607104d4c616d732e11c7c2..bb4b69fc38851e9cb2cc6264f53053aa7d74f1d6 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -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);