Introduce debug events for promises.

test/mjsunit/es6/debug-promises-new-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 new_promise;
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.PromiseEvent) return;
+  try {
+    assertTrue(event_data.resolver().isFunction());
+    assertEquals(resolver, event_data.resolver().value());
+    assertTrue(event_data.resolver().resolved());
+    assertEquals("resolver", event_data.resolver().name());
+    assertTrue(event_data.resolver().source().indexOf("Token") > 0);
+
+    assertTrue(event_data.promise().isPromise());
+    new_promise = event_data.promise().value();
+    assertEquals("pending", event_data.promise().status());
+  } catch (e) {
+    print(e + e.stack)
+    exception = e;
+  }
+}
+
+Debug.setListener(listener);
+
+function resolver(resolve, reject) {
+  resolve();  // Token
+}
+
+var p = new Promise(resolver);
+assertEquals(new_promise, p);
+
+assertNull(exception);
+Debug.setListener(null);