[api] Prototype WeakRef implementation

src/heap/heap.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_HEAP_HEAP_H_
 #define V8_HEAP_HEAP_H_
 
 #include <cmath>
 #include <map>
 
@@ skipping 181 matching lines @@
   V(Object, instanceof_cache_answer, InstanceofCacheAnswer)                    \
   /* Lists and dictionaries */                                                 \
   V(NameDictionary, empty_properties_dictionary, EmptyPropertiesDictionary)    \
   V(NameDictionary, public_symbol_table, PublicSymbolTable)                    \
   V(NameDictionary, api_symbol_table, ApiSymbolTable)                          \
   V(NameDictionary, api_private_symbol_table, ApiPrivateSymbolTable)           \
   V(Object, script_list, ScriptList)                                           \
   V(UnseededNumberDictionary, code_stubs, CodeStubs)                           \
   V(FixedArray, materialized_objects, MaterializedObjects)                     \
   V(FixedArray, microtask_queue, MicrotaskQueue)                               \
+  V(FixedArray, weak_refs, WeakRefs)                                           \
   V(FixedArray, detached_contexts, DetachedContexts)                           \
   V(ArrayList, retained_maps, RetainedMaps)                                    \
   V(WeakHashTable, weak_object_to_code_table, WeakObjectToCodeTable)           \
   /* weak_new_space_object_to_code_list is an array of weak cells, where */    \
   /* slots with even indices refer to the weak object, and the subsequent */   \
   /* slots refer to the code with the reference to the weak object. */         \
   V(ArrayList, weak_new_space_object_to_code_list,                             \
     WeakNewSpaceObjectToCodeList)                                              \
   /* List to hold onto feedback vectors that we need for code coverage */      \
   V(Object, code_coverage_list, CodeCoverageList)                              \
@@ skipping 2440 matching lines @@
   friend class LargeObjectSpace;
   friend class NewSpace;
   friend class PagedSpace;
   DISALLOW_COPY_AND_ASSIGN(AllocationObserver);
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_HEAP_HEAP_H_