Allow embedder to set promise internal field count

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 3838 matching lines @@
 
   ScriptOrigin GetScriptOrigin() const;
   V8_INLINE static Function* Cast(Value* obj);
   static const int kLineOffsetNotFound;
 
  private:
   Function();
   static void CheckCast(Value* obj);
 };
 
+#ifndef V8_PROMISE_INTERNAL_FIELD_COUNT
+// The number of required internal fields can be defined by embedder.
+#define V8_PROMISE_INTERNAL_FIELD_COUNT 0
+#endif
 
 /**
  * An instance of the built-in Promise constructor (ES6 draft).
  */
 class V8_EXPORT Promise : public Object {
  public:
   /**
    * State of the promise. Each value corresponds to one of the possible values
    * of the [[PromiseState]] field.
    */
@@ skipping 61 matching lines @@
    */
   Local<Value> Result();
 
   /**
    * Returns the value of the [[PromiseState]] field.
    */
   PromiseState State();
 
   V8_INLINE static Promise* Cast(Value* obj);
 
+  static const int kEmbedderFieldCount = V8_PROMISE_INTERNAL_FIELD_COUNT;
+
  private:
   Promise();
   static void CheckCast(Value* obj);
 };
 
 /**
  * An instance of a Property Descriptor, see Ecma-262 6.2.4.
  *
  * Properties in a descriptor are present or absent. If you do not set
  * `enumerable`, `configurable`, and `writable`, they are absent. If `value`,
@@ skipping 6151 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // INCLUDE_V8_H_