[api] add API for Promise status and result.

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 3681 matching lines @@
   Function();
   static void CheckCast(Value* obj);
 };
 
 
 /**
  * An instance of the built-in Promise constructor (ES6 draft).
  */
 class V8_EXPORT Promise : public Object {
  public:
+  enum PromiseStatus { kPending, kFulfilled, kRejected };

[jochen (gone - plz use gerrit), 2016/12/20 07:49:52]

why not an enum class?

also, please add a comment explaining what the values mean

[Yang, 2016/12/20 11:38:27]

enum class requires static_cast all over the place because we use this enum as
an integer value when storing as a smi.

+
   class V8_EXPORT Resolver : public Object {
    public:
     /**
      * Create a new resolver, along with an associated promise in pending state.
      */
     static V8_DEPRECATE_SOON("Use maybe version",
                              Local<Resolver> New(Isolate* isolate));
     static V8_WARN_UNUSED_RESULT MaybeLocal<Resolver> New(
         Local<Context> context);
 
@@ skipping 36 matching lines @@
                 Local<Promise> Then(Local<Function> handler));
   V8_WARN_UNUSED_RESULT MaybeLocal<Promise> Then(Local<Context> context,
                                                  Local<Function> handler);
 
   /**
    * Returns true if the promise has at least one derived promise, and
    * therefore resolve/reject handlers (including default handler).
    */
   bool HasHandler();
 
+  MaybeLocal<Value> Result();

[jochen (gone - plz use gerrit), 2016/12/20 07:49:52]

please also add a comment to document this API (and Status() below)

[Yang, 2016/12/20 11:38:27]

Done.

+
+  PromiseStatus Status();
+
   V8_INLINE static Promise* Cast(Value* obj);
 
  private:
   Promise();
   static void CheckCast(Value* obj);
 };
 
 /**
  * An instance of a Property Descriptor, see Ecma-262 6.2.4.
  *
@@ skipping 5963 matching lines @@
  */
 
 
 }  // namespace v8
 
 
 #undef TYPE_CHECK
 
 
 #endif  // INCLUDE_V8_H_