Clear next map word when folding allocations into js arrays.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 4685dc7d314cf4c4a99f6fcdd69b0c8455f35704..988f1ab636fc6205edc197a99201f63ef8caef37 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -5776,7 +5776,6 @@ class Map: public HeapObject {
     set_bit_field3(EnumLengthBits::update(bit_field3(), length));
   }
 
-  inline bool CanTrackAllocationSite();
   inline bool owns_descriptors();
   inline void set_owns_descriptors(bool is_shared);
   inline bool is_observed();
@@ -7845,6 +7844,7 @@ class AllocationSite: public Struct {
   static inline AllocationSiteMode GetMode(
       ElementsKind boilerplate_elements_kind);
   static inline AllocationSiteMode GetMode(ElementsKind from, ElementsKind to);
+  static inline bool CanTrack(InstanceType type);
 
   static const int kTransitionInfoOffset = HeapObject::kHeaderSize;
   static const int kWeakNextOffset = kTransitionInfoOffset + kPointerSize;