[api] Prototype WeakRef implementation

src/api.cc

 // 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.
 
 #include "src/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 3537 matching lines @@
 VALUE_IS_SPECIFIC_TYPE(ArgumentsObject, Arguments)
 VALUE_IS_SPECIFIC_TYPE(BooleanObject, Boolean)
 VALUE_IS_SPECIFIC_TYPE(NumberObject, Number)
 VALUE_IS_SPECIFIC_TYPE(StringObject, String)
 VALUE_IS_SPECIFIC_TYPE(SymbolObject, Symbol)
 VALUE_IS_SPECIFIC_TYPE(Date, Date)
 VALUE_IS_SPECIFIC_TYPE(Map, Map)
 VALUE_IS_SPECIFIC_TYPE(Set, Set)
 VALUE_IS_SPECIFIC_TYPE(WeakMap, WeakMap)
 VALUE_IS_SPECIFIC_TYPE(WeakSet, WeakSet)
+VALUE_IS_SPECIFIC_TYPE(WeakRef, WeakRef)
 
 #undef VALUE_IS_SPECIFIC_TYPE
 
 
 bool Value::IsBoolean() const {
   return Utils::OpenHandle(this)->IsBoolean();
 }
 
 
 bool Value::IsExternal() const {
@@ skipping 6895 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8