Convert mac/ios TaskQueue implementation to pimpl convention.

webrtc/rtc_base/task_queue.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_RTC_BASE_TASK_QUEUE_H_
 #define WEBRTC_RTC_BASE_TASK_QUEUE_H_
 
 #include <list>
 #include <memory>
 #include <queue>
 #include <type_traits>
 
-#if defined(WEBRTC_MAC)
-#include <dispatch/dispatch.h>
-#endif
-
 #include "webrtc/rtc_base/constructormagic.h"
 #include "webrtc/rtc_base/criticalsection.h"
 #include "webrtc/rtc_base/scoped_ref_ptr.h"
 
 namespace rtc {
 
 // Base interface for asynchronously executed tasks.
 // The interface basically consists of a single function, Run(), that executes
 // on the target queue.  For more details see the Run() method and TaskQueue.
 class QueuedTask {
@@ skipping 196 matching lines @@
   }
 
   template <class Closure1, class Closure2>
   void PostTaskAndReply(const Closure1& task, const Closure2& reply) {
     PostTaskAndReply(
         std::unique_ptr<QueuedTask>(new ClosureTask<Closure1>(task)),
         std::unique_ptr<QueuedTask>(new ClosureTask<Closure2>(reply)));
   }
 
  private:
-#if defined(WEBRTC_MAC)
-  struct QueueContext;
-  struct TaskContext;
-  struct PostTaskAndReplyContext;
-  dispatch_queue_t queue_;
-  QueueContext* const context_;
-#else
   class Impl;
   const scoped_refptr<Impl> impl_;
-#endif
 
   RTC_DISALLOW_COPY_AND_ASSIGN(TaskQueue);
 };
 
 }  // namespace rtc
 
 #endif  // WEBRTC_RTC_BASE_TASK_QUEUE_H_