Add data pipe wrappers to be used to implement serial receive.

device/serial/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 "device/serial/async_waiter.h"
+
+namespace device {
+
+AsyncWaiter::AsyncWaiter(mojo::Handle handle,
+                         MojoHandleSignals signals,
+                         const Callback& callback)
+    : waiter_(mojo::Environment::GetDefaultAsyncWaiter()),
+      id_(0),
+      callback_(callback) {
+  id_ = waiter_->AsyncWait(handle.value(),
+                           signals,
+                           MOJO_DEADLINE_INDEFINITE,
+                           &AsyncWaiter::WaitComplete,
+                           this);
+}
+
+AsyncWaiter::~AsyncWaiter() {
+  if (id_)
+    waiter_->CancelWait(id_);
+}
+
+// static
+void AsyncWaiter::WaitComplete(void* waiter, MojoResult result) {
+  static_cast<AsyncWaiter*>(waiter)->WaitCompleteInternal(result);
+}
+
+void AsyncWaiter::WaitCompleteInternal(MojoResult result) {
+  id_ = 0;
+  callback_.Run(result);
+}
+
+}  // namespace device