Revert of New task queueing primitive for async tasks: TaskQueue.

webrtc/base/task_queue_posix.h

-/*
- *  Copyright 2016 The WebRTC Project Authors. All rights reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#ifndef WEBRTC_BASE_TASK_QUEUE_POSIX_H_
-#define WEBRTC_BASE_TASK_QUEUE_POSIX_H_
-
-#include <pthread.h>
-
-namespace rtc {
-
-class TaskQueue;
-
-namespace internal {
-
-class AutoSetCurrentQueuePtr {
- public:
-  explicit AutoSetCurrentQueuePtr(TaskQueue* q);
-  ~AutoSetCurrentQueuePtr();
-
- private:
-  TaskQueue* const prev_;
-};
-
-pthread_key_t GetQueuePtrTls();
-
-}  // namespace internal
-}  // namespace rtc
-
-#endif  // WEBRTC_BASE_TASK_QUEUE_POSIX_H_