Introduce more debug events for promises.

test/mjsunit/es6/debug-promises-update-parent-event.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
+
+Debug = debug.Debug;
+
+var exception = null;
+var promise, parentPromise;
+var counter = 0;
+
+function listener(event, exec_state, event_data, data) {
+  if (!(event_data instanceof debug.UpdatePromiseParentEvent)) return;
+  try {
+    counter++;
+
+    assertTrue(event_data.promise().isPromise());
+    promise = event_data.promise().value();
+
+    assertTrue(event_data.parentPromise().isPromise());
+    parentPromise = event_data.parentPromise().value();

[Yang, 2014/07/24 08:43:58]

how about, instead of using a single value for parentPromise, log the parent
promises into an array, and compare the array with the expectation?

[Alexandra Mikhaylova, 2014/07/24 09:18:37]

Thanks, done. Added an array of promise/parent pairs.

+  } catch (e) {
+    print(e + e.stack);
+    exception = e;
+  }
+}
+
+Debug.setListener(listener);
+
+var p1 = new Promise(function(resolve, reject) { resolve(1) });
+var p2 = p1.then().then();
+var p3 = p2.then();

[Yang, 2014/07/24 08:43:58]

Instead of a chain of promises, how about having a tree of promises? like adding
var p4 = p1.then();

[Alexandra Mikhaylova, 2014/07/24 09:18:37]

Done.

+assertSame(parentPromise, p2);
+assertSame(promise, p3);
+assertEquals(3, counter);
+
+assertNull(exception);
+Debug.setListener(null);