Introduce more debug events for promises.

test/mjsunit/es6/debug-promises-update-status-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, status, value;
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.PromiseEvent) return;
+  try {
+    if (event_data instanceof debug.UpdatePromiseStatusEvent) {
+      assertTrue(event_data.promise().isPromise());
+      promise = event_data.promise().value();
+
+      status = event_data.status();
+
+      value = event_data.value().value();
+    }
+  } catch (e) {
+    print(e + e.stack);
+    exception = e;
+  }
+}
+
+Debug.setListener(listener);
+
+var p1 = new Promise(function(resolve, reject) { resolve(1) });
+assertSame(promise, p1);
+assertEquals(status, 1);
+assertEquals(value, 1);
+
+var p2 = new Promise(function(resolve, reject) { reject(2) });
+assertSame(promise, p2);
+assertEquals(status, -1);
+assertEquals(value, 2);
+
+assertNull(exception);
+Debug.setListener(null);