[api] Bring back finalizers on global handles

include/v8.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.
 
 /** \mainpage V8 API Reference Guide
  *
  * V8 is Google's open source JavaScript engine.
  *
  * This set of documents provides reference material generated from the
  * V8 header file, include/v8.h.
@@ skipping 462 matching lines @@
   Isolate* isolate_;
   P* parameter_;
   Local<T> handle_;
 };
 
 
 // TODO(dcarney): delete this with WeakCallbackData
 template <class T>
 using PhantomCallbackData = WeakCallbackInfo<T>;
 
-
-enum class WeakCallbackType { kParameter, kInternalFields };
-
+// kParameter will pass a void* parameter back to the callback, kInternalFields
+// will pass the first two internal fields back to the callback, kFinalizer
+// will pass a void* parameter back, but is invoked before the object is
+// actually collected, so it can be resurrected. In the last case, it is not
+// possible to request a second pass callback.
+enum class WeakCallbackType { kParameter, kInternalFields, kFinalizer };
 
 /**
  * An object reference that is independent of any handle scope.  Where
  * a Local handle only lives as long as the HandleScope in which it was
  * allocated, a PersistentBase handle remains valid until it is explicitly
  * disposed.
  *
  * A persistent handle contains a reference to a storage cell within
  * the v8 engine which holds an object value and which is updated by
  * the garbage collector whenever the object is moved.  A new storage
@@ skipping 8274 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // INCLUDE_V8_H_