Mojo: Move waiting APIs to public library

mojo/edk/system/awakable.h

-// Copyright 2013 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_AWAKABLE_H_
-#define MOJO_EDK_SYSTEM_AWAKABLE_H_
-
-#include <stdint.h>
-
-#include "mojo/edk/system/system_impl_export.h"
-#include "mojo/public/c/system/types.h"
-
-namespace mojo {
-namespace edk {
-
-// An interface that may be waited on |AwakableList|.
-class MOJO_SYSTEM_IMPL_EXPORT Awakable {
- public:
-  // |Awake()| must satisfy the following contract:
-  // * As this is called from any thread, this must be thread-safe.
-  // * As this is called inside a lock, this must not call anything that takes
-  //   "non-terminal" locks, i.e., those which are always safe to take.
-  // This should return false if this must not be called again for the same
-  // reason (e.g., for the same call to |AwakableList::Add()|).
-  virtual bool Awake(MojoResult result, uintptr_t context) = 0;
-
- protected:
-  Awakable() {}
-};
-
-}  // namespace edk
-}  // namespace mojo
-
-#endif  // MOJO_EDK_SYSTEM_AWAKABLE_H_