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

base/task_runner.h

 // 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_TASK_RUNNER_H_
 #define BASE_TASK_RUNNER_H_
 
 #include <stddef.h>
 
 #include "base/base_export.h"
@@ skipping 43 matching lines @@
 //   - A TaskRunner that stores the list of posted tasks and has a
 //     method Run() that runs each runnable task in random order.
 class BASE_EXPORT TaskRunner
     : public RefCountedThreadSafe<TaskRunner, TaskRunnerTraits> {
  public:
   // Posts the given task to be run.  Returns true if the task may be
   // run at some point in the future, and false if the task definitely
   // will not be run.
   //
   // Equivalent to PostDelayedTask(from_here, task, 0).
-  bool PostTask(const tracked_objects::Location& from_here,
-                const Closure& task);
+  bool PostTask(const tracked_objects::Location& from_here, Closure task);
 
   // Like PostTask, but tries to run the posted task only after
   // |delay_ms| has passed.
   //
   // It is valid for an implementation to ignore |delay_ms|; that is,
   // to have PostDelayedTask behave the same as PostTask.
   virtual bool PostDelayedTask(const tracked_objects::Location& from_here,
-                               const Closure& task,
+                               Closure task,
                                base::TimeDelta delay) = 0;
 
   // Returns true if the current thread is a thread on which a task
   // may be run, and false if no task will be run on the current
   // thread.
   //
   // It is valid for an implementation to always return true, or in
   // general to use 'true' as a default value.
   virtual bool RunsTasksOnCurrentThread() const = 0;
 
@@ skipping 58 matching lines @@
   virtual void OnDestruct() const;
 };
 
 struct BASE_EXPORT TaskRunnerTraits {
   static void Destruct(const TaskRunner* task_runner);
 };
 
 }  // namespace base
 
 #endif  // BASE_TASK_RUNNER_H_