Pass Callback to TaskRunner by value and consume it on invocation (1)

content/child/worker_thread_registry.h

 // Copyright 2014 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 CONTENT_CHILD_WORKER_THREAD_REGISTRY_H_
 #define CONTENT_CHILD_WORKER_THREAD_REGISTRY_H_
 
 #include <map>
 
-#include "base/callback_forward.h"
+#include "base/callback.h"
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/platform_thread.h"
 #include "content/common/content_export.h"
 #include "content/public/child/worker_thread.h"
 
 namespace base {
 class TaskRunner;
 }
 
 namespace content {
 
 class CONTENT_EXPORT WorkerThreadRegistry {
  public:
   WorkerThreadRegistry();
 
-  int PostTaskToAllThreads(const base::Closure& task);
+  int PostTaskToAllThreads(base::Closure task);
   static WorkerThreadRegistry* Instance();
 
   void DidStartCurrentWorkerThread();
   void WillStopCurrentWorkerThread();
 
   // Always returns a non-null task runner regardless of whether the
   // corresponding worker thread is gone or not. If the thread is already gone
   // the tasks posted onto the task runner will be silently discarded.
   base::TaskRunner* GetTaskRunnerFor(int worker_id);
 
  private:
   friend class WorkerThread;
   friend class WorkerThreadRegistryTest;
 
-  bool PostTask(int id, const base::Closure& task);
+  bool PostTask(int id, base::Closure task);
 
   using IDToTaskRunnerMap = std::map<base::PlatformThreadId, base::TaskRunner*>;
 
   ~WorkerThreadRegistry();
 
   // It is possible for an IPC message to arrive for a worker thread that has
   // already gone away. In such cases, it is still necessary to provide a
   // task-runner for that particular thread, because otherwise the message will
   // end up being handled as per usual in the main-thread, causing incorrect
   // results. |task_runner_for_dead_worker_| is used to handle such messages,
   // which silently discards all the tasks it receives.
   scoped_refptr<base::TaskRunner> task_runner_for_dead_worker_;
 
   IDToTaskRunnerMap task_runner_map_;
   base::Lock task_runner_map_lock_;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_CHILD_WORKER_THREAD_REGISTRY_H_