Replace Closure in TaskRunner::PostTask with OneShotCallback

base/callback_forward.h

 // Copyright (c) 2011 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 BASE_CALLBACK_FORWARD_H_
 #define BASE_CALLBACK_FORWARD_H_
 
 namespace base {
 namespace internal {
 
@@ skipping 14 matching lines @@
 
 template <typename Signature,
           internal::CopyMode copy_mode = internal::CopyMode::Copyable,
           internal::RepeatMode repeat_mode = internal::RepeatMode::Repeating>
 class Callback;
 
 // Syntactic sugar to make Callback<void()> easier to declare since it
 // will be used in a lot of APIs with delayed execution.
 using Closure = Callback<void()>;
 
-namespace internal {
-
 template <typename Signature>
 using OnceCallback = Callback<Signature,
                               internal::CopyMode::MoveOnly,
                               internal::RepeatMode::Once>;
 template <typename Signature>
 using RepeatingCallback = Callback<Signature,
                                    internal::CopyMode::Copyable,
                                    internal::RepeatMode::Repeating>;
 using OnceClosure = OnceCallback<void()>;
 using RepeatingClosure = RepeatingCallback<void()>;
 
-}  // namespace internal
 }  // namespace base
 
 #endif  // BASE_CALLBACK_FORWARD_H_