Add embedder::AsyncWait()

mojo/edk/system/async_waiter.cc

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "mojo/edk/system/async_waiter.h"
+
+namespace mojo {
+namespace system {
+
+AsyncWaiter::AsyncWaiter(AwakeCallback callback) : callback_(callback) {
+}
+
+AsyncWaiter::~AsyncWaiter() {
+}
+
+bool AsyncWaiter::Awake(MojoResult result, uintptr_t context) {
+  callback_.Run(result);
+  delete this;
+  return false;
+}
+
+}  // namespace system
+}  // namespace mojo