Expose promise status through promise mirror.

src/promise.js

Index: src/promise.js
diff --git a/src/promise.js b/src/promise.js
index f77fc5c197b982c19fea7253e1e7632d319e1d78..b87f9d65f93e8420a51257b36b80355354e1a938 100644
--- a/src/promise.js
+++ b/src/promise.js
@@ -338,3 +338,20 @@ function SetUpPromise() {
 }
 
 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);
+}