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 result = [];
+
+function listener(event, exec_state, event_data, data) {
+  if (!(event_data instanceof debug.UpdatePromiseParentEvent)) return;
+  try {
+    assertTrue(event_data.promise().isPromise());
+    assertTrue(event_data.parentPromise().isPromise());
+    result.push({ promise: event_data.promise().value(),
+                  parentPromise: event_data.parentPromise().value() });
+  } 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();
+var p4 = p1.then();
+
+assertEquals(4, result.length);
+assertSame(p1, result[0].parentPromise);
+assertSame(p2, result[1].promise);
+assertSame(p3, result[2].promise);
+assertSame(p2, result[2].parentPromise);
+assertSame(p4, result[3].promise);
+assertSame(p1, result[3].parentPromise);
+
+assertNull(exception);
+Debug.setListener(null);