Use weak cells in map checks in polymorphic ICs.

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index d17d0d1ef1c851e08dca8eb5b1cfa8a812f04660..a45eef16980b8bd2b7dec530ad7a1677540299b2 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -6190,6 +6190,8 @@ class Map: public HeapObject {
 
   bool IsMapInArrayPrototypeChain();
 
+  static Handle<WeakCell> WeakCellForMap(Handle<Map> map);
+
   // Dispatched behavior.
   DECLARE_PRINTER(Map)
   DECLARE_VERIFIER(Map)
@@ -8025,6 +8027,7 @@ class CodeCache: public Struct {
  public:
   DECL_ACCESSORS(default_cache, FixedArray)
   DECL_ACCESSORS(normal_type_cache, Object)
+  DECL_ACCESSORS(weak_cell_cache, Object)
 
   // Add the code object to the cache.
   static void Update(
@@ -8052,7 +8055,8 @@ class CodeCache: public Struct {
   static const int kDefaultCacheOffset = HeapObject::kHeaderSize;
   static const int kNormalTypeCacheOffset =
       kDefaultCacheOffset + kPointerSize;
-  static const int kSize = kNormalTypeCacheOffset + kPointerSize;
+  static const int kWeakCellCacheOffset = kNormalTypeCacheOffset + kPointerSize;
+  static const int kSize = kWeakCellCacheOffset + kPointerSize;
 
  private:
   static void UpdateDefaultCache(