Make new TaskRunner, SequencedTaskRunner, and SingleThreadTaskRunner interfaces

base/message_loop_helpers.h

-// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Copyright (c) 2012 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_MESSAGE_LOOP_HELPERS_H_
 #define BASE_MESSAGE_LOOP_HELPERS_H_
 #pragma once
 
-#include "base/basictypes.h"
-
-namespace tracked_objects {
-class Location;
-}
-
-namespace base {
-
-namespace subtle {
-template <class T, class R> class DeleteHelperInternal;
-template <class T, class R> class ReleaseHelperInternal;
-}
-
-// Template helpers which use a function indirection to erase T from the
-// function signature while still remembering it so we can call the correct
-// destructor/release function.
-// We use this trick so we don't need to include bind.h in a header file like
-// message_loop.h. We also wrap the helpers in a templated class to make it
-// easier for users of DeleteSoon to declare the helper as a friend.
-template <class T>
-class DeleteHelper {
- private:
-  template <class T2, class R> friend class subtle::DeleteHelperInternal;
-
-  static void DoDelete(const void* object) {
-    delete reinterpret_cast<const T*>(object);
-  }
-
-  DISALLOW_COPY_AND_ASSIGN(DeleteHelper);
-};
-
-template <class T>
-class ReleaseHelper {
- private:
-  template <class T2, class R> friend class subtle::ReleaseHelperInternal;
-
-  static void DoRelease(const void* object) {
-    reinterpret_cast<const T*>(object)->Release();
-  }
-
-  DISALLOW_COPY_AND_ASSIGN(ReleaseHelper);
-};
-
-namespace subtle {
-
-// An internal MessageLoop-like class helper for DeleteHelper and ReleaseHelper.
-// We don't want to expose the Do*() functions directly directly since the void*
-// argument makes it possible to pass/ an object of the wrong type to delete.
-// Instead, we force callers to go through these internal helpers for type
-// safety. MessageLoop-like classes which expose DeleteSoon or ReleaseSoon
-// methods should friend the appropriate helper and implement a corresponding
-// *Internal method with the following signature:
-// bool(const tracked_objects::Location&,
-//      void(*function)(const void*),
-//      void* object)
-// An implementation of this function should simply create a base::Closure
-// from (function, object) and return the result of posting the task.
-template <class T, class ReturnType>
-class DeleteHelperInternal {
- public:
-  template <class MessageLoopType>
-  static ReturnType DeleteOnMessageLoop(
-      MessageLoopType* message_loop,
-      const tracked_objects::Location& from_here,
-      const T* object) {
-    return message_loop->DeleteSoonInternal(from_here,
-                                            &DeleteHelper<T>::DoDelete,
-                                            object);
-  }
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(DeleteHelperInternal);
-};
-
-template <class T, class ReturnType>
-class ReleaseHelperInternal {
- public:
-  template <class MessageLoopType>
-  static ReturnType ReleaseOnMessageLoop(
-      MessageLoopType* message_loop,
-      const tracked_objects::Location& from_here,
-      const T* object) {
-    return message_loop->ReleaseSoonInternal(from_here,
-                                             &ReleaseHelper<T>::DoRelease,
-                                             object);
-  }
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(ReleaseHelperInternal);
-};
-
-}  // namespace subtle
-
-}  // namespace base
+// TODO(akalin): Change all includers of message_loop_helpers.h to
+// include sequenced_task_runner_helpers.h instead.
+#include "base/sequenced_task_runner_helpers.h"
 
 #endif  // BASE_MESSAGE_LOOP_HELPERS_H_