Implement aging of maps embedded in optimized code.

src/heap/heap.h

Index: src/heap/heap.h
diff --git a/src/heap/heap.h b/src/heap/heap.h
index 184cb42b2ee8f6ef9043b1892fb65c693ab51f9f..49519a267671d7aa615c379ff312d958973b4db9 100644
--- a/src/heap/heap.h
+++ b/src/heap/heap.h
@@ -832,6 +832,8 @@ class Heap {
 
   Object* weak_object_to_code_table() { return weak_object_to_code_table_; }
 
+  Object* embedded_map_cache() { return embedded_map_cache_; }
+
   void set_encountered_weak_collections(Object* weak_collection) {
     encountered_weak_collections_ = weak_collection;
   }
@@ -861,6 +863,7 @@ class Heap {
   // from start to end.
   void IterateAndMarkPointersToFromSpace(Address start, Address end,
                                          ObjectSlotCallback callback);
+  void IterateEmbeddedMapCache(ObjectVisitor* v);
 
   // Returns whether the object resides in new space.
   inline bool InNewSpace(Object* object);
@@ -1398,8 +1401,12 @@ class Heap {
     set_weak_object_to_code_table(undefined_value());
   }
 
+  void InitializeEmbeddedMapCache() { embedded_map_cache_ = undefined_value(); }
+
   void EnsureWeakObjectToCodeTable();
 
+  void CacheEmbeddedMap(Handle<Map> map);
+
   static void FatalProcessOutOfMemory(const char* location,
                                       bool take_snapshot = false);
 
@@ -1583,6 +1590,8 @@ class Heap {
   // start.
   Object* weak_object_to_code_table_;
 
+  Object* embedded_map_cache_;
+
   // List of encountered weak collections (JSWeakMap and JSWeakSet) during
   // marking. It is initialized during marking, destroyed after marking and
   // contains Smi(0) while marking is not active.
@@ -2001,6 +2010,8 @@ class Heap {
     return &weak_object_to_code_table_;
   }
 
+  Object** embedded_map_cache_address() { return &embedded_map_cache_; }
+
   inline void UpdateAllocationsHash(HeapObject* object);
   inline void UpdateAllocationsHash(uint32_t value);
   inline void PrintAlloctionsHash();