Expose promise status through promise mirror.

src/promise.js

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 320 matching lines @@
     "resolve", PromiseCast
   ]);
   InstallFunctions($Promise.prototype, DONT_ENUM, [
     "chain", PromiseChain,
     "then", PromiseThen,
     "catch", PromiseCatch
   ]);
 }
 
 SetUpPromise();
+
+// Functions to expose promise details to the debugger.
+function GetPromiseStatus(promise) {
+  return GET_PRIVATE(promise, promiseStatus);
+}
+
+function GetPromiseOnResolve(promise) {
+  return GET_PRIVATE(promise, promiseOnResolve);
+}
+
+function GetPromiseOnReject(promise) {
+  return GET_PRIVATE(promise, promiseOnReject);
+}
+
+function GetPromiseValue(promise) {
+  return GET_PRIVATE(promise, promiseValue);
+}