Use %DebugGetProperty in debug mirror to check for Promise.

test/mjsunit/es6/mirror-promises.js

 // Copyright 2014 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.
 
 // Flags: --expose-debug-as debug --harmony-promises
 // Test the mirror object for promises.
 
 function MirrorRefCache(json_refs) {
   var tmp = eval('(' + json_refs + ')');
   this.refs_ = [];
@@ skipping 21 matching lines @@
   assertTrue(mirror instanceof debug.PromiseMirror);
 
   // Check the mirror properties.
   assertEquals(status, mirror.status());
   assertTrue(mirror.isPromise());
   assertEquals('promise', mirror.type());
   assertFalse(mirror.isPrimitive());
   assertEquals("Object", mirror.className());
   assertEquals("#<Promise>", mirror.toText());
   assertSame(promise, mirror.value());
-  assertEquals(value, mirror.promiseValue());
+  assertTrue(mirror.promiseValue() instanceof debug.Mirror);
+  assertEquals(value, mirror.promiseValue().value());
 
   // Parse JSON representation and check.
   var fromJSON = eval('(' + json + ')');
   assertEquals('promise', fromJSON.type);
   assertEquals('Object', fromJSON.className);
   assertEquals('function', refs.lookup(fromJSON.constructorFunction.ref).type);
   assertEquals('Promise', refs.lookup(fromJSON.constructorFunction.ref).name);
   assertEquals(status, fromJSON.status);
-  assertEquals(value, fromJSON.promiseValue);
+  assertEquals(value, refs.lookup(fromJSON.promiseValue.ref).value);
 }
 
 // Test a number of different promises.
 var resolved = new Promise(function(resolve, reject) { resolve() });
 var rejected = new Promise(function(resolve, reject) { reject() });
 var pending = new Promise(function(resolve, reject) {});
 
 testPromiseMirror(resolved, "resolved", undefined);
 testPromiseMirror(rejected, "rejected", undefined);
 testPromiseMirror(pending, "pending", undefined);
@@ skipping 17 matching lines @@
 assertEquals(1, ip[1].value().value());
 
 var m2 = debug.MakeMirror(new Promise(function(resolve, reject) { reject(2) }));
 ip = m2.internalProperties();
 assertEquals("rejected", ip[0].value().value());
 assertEquals(2, ip[1].value().value());
 
 var m3 = debug.MakeMirror(new Promise(function(resolve, reject) { }));
 ip = m3.internalProperties();
 assertEquals("pending", ip[0].value().value());
-assertEquals("undefined", typeof(ip[1].value().value()));
+assertEquals("undefined", typeof(ip[1].value().value()));