[api] add API for Promise status and result.

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 7271 matching lines @@
   i::Isolate* isolate = promise->GetIsolate();
   LOG_API(isolate, Promise, HasRejectHandler);
   ENTER_V8(isolate);
   if (promise->IsJSPromise()) {
     i::Handle<i::JSPromise> js_promise = i::Handle<i::JSPromise>::cast(promise);
     return js_promise->has_handler();
   }
   return false;
 }
 
+Local<Value> Promise::Result() {
+  i::Handle<i::JSReceiver> promise = Utils::OpenHandle(this);
+  i::Isolate* isolate = promise->GetIsolate();
+  LOG_API(isolate, Promise, Result);
+  i::Handle<i::JSPromise> js_promise = i::Handle<i::JSPromise>::cast(promise);
+  Utils::ApiCheck(js_promise->status() != kPending, "v8_Promise_Result",
+                  "Promise is still pending");
+  i::Handle<i::Object> result(js_promise->result(), isolate);
+  return Utils::ToLocal(result);
+}
+
+Promise::PromiseState Promise::State() {
+  i::Handle<i::JSReceiver> promise = Utils::OpenHandle(this);
+  i::Isolate* isolate = promise->GetIsolate();
+  LOG_API(isolate, Promise, Status);
+  i::Handle<i::JSPromise> js_promise = i::Handle<i::JSPromise>::cast(promise);
+  return static_cast<PromiseState>(js_promise->status());
+}
 
 Local<Object> Proxy::GetTarget() {
   i::Handle<i::JSProxy> self = Utils::OpenHandle(this);
   i::Handle<i::JSReceiver> target(self->target());
   return Utils::ToLocal(target);
 }
 
 
 Local<Value> Proxy::GetHandler() {
   i::Handle<i::JSProxy> self = Utils::OpenHandle(this);
@@ skipping 2602 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