Add embedder::AsyncWait()

mojo/edk/system/async_waiter.h

Index: mojo/edk/system/async_waiter.h
diff --git a/mojo/edk/system/async_waiter.h b/mojo/edk/system/async_waiter.h
new file mode 100644
index 0000000000000000000000000000000000000000..da412c032659f7bc9c36d2fe8a194c3a4014a7af
--- /dev/null
+++ b/mojo/edk/system/async_waiter.h
@@ -0,0 +1,38 @@
+// 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.
+
+#ifndef MOJO_EDK_SYSTEM_ASYNC_WAITER_H_
+#define MOJO_EDK_SYSTEM_ASYNC_WAITER_H_
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "mojo/edk/system/awakable.h"
+#include "mojo/edk/system/system_impl_export.h"
+#include "mojo/public/c/system/types.h"
+
+namespace mojo {
+namespace system {
+
+// An |Awakable| implementation that just calls a given callback object.
+class MOJO_SYSTEM_IMPL_EXPORT AsyncWaiter final : public Awakable {
+ public:
+  typedef base::Callback<void(MojoResult)> AwakeCallback;
+
+  // |callback| must satisfy the same contract as |Awakable::Awake()|.
+  explicit AsyncWaiter(AwakeCallback callback);
+  virtual ~AsyncWaiter();
+
+ private:
+  // |Awakable| implementation:
+  bool Awake(MojoResult result, uintptr_t context) override;
+
+  AwakeCallback callback_;
+
+  DISALLOW_COPY_AND_ASSIGN(AsyncWaiter);
+};
+
+}  // namespace system
+}  // namespace mojo
+
+#endif  // MOJO_EDK_SYSTEM_ASYNC_WAITER_H_