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

base/deferred_sequenced_task_runner.h

 // Copyright (c) 2013 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_DEFERRED_SEQUENCED_TASK_RUNNER_H_
 #define BASE_DEFERRED_SEQUENCED_TASK_RUNNER_H_
 
 #include <vector>
 
 #include "base/base_export.h"
@@ skipping 10 matching lines @@
 
 // A DeferredSequencedTaskRunner is a subclass of SequencedTaskRunner that
 // queues up all requests until the first call to Start() is issued.
 class BASE_EXPORT DeferredSequencedTaskRunner : public SequencedTaskRunner {
  public:
   explicit DeferredSequencedTaskRunner(
       scoped_refptr<SequencedTaskRunner> target_runner);
 
   // TaskRunner implementation
   bool PostDelayedTask(const tracked_objects::Location& from_here,
-                       const Closure& task,
+                       Closure task,
                        TimeDelta delay) override;
   bool RunsTasksOnCurrentThread() const override;
 
   // SequencedTaskRunner implementation
   bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
-                                  const Closure& task,
+                                  Closure task,
                                   TimeDelta delay) override;
 
   // Start the execution - posts all queued tasks to the target executor. The
   // deferred tasks are posted with their initial delay, meaning that the task
   // execution delay is actually measured from Start.
   // Fails when called a second time.
   void Start();
 
  private:
   struct DeferredTask  {
     DeferredTask();
-    DeferredTask(const DeferredTask& other);
+    DeferredTask(DeferredTask&& other);
     ~DeferredTask();
+    DeferredTask& operator=(DeferredTask&& other);
 
     tracked_objects::Location posted_from;
     Closure task;
     // The delay this task was initially posted with.
     TimeDelta delay;
     bool is_non_nestable;
   };
 
   ~DeferredSequencedTaskRunner() override;
 
   // Creates a |Task| object and adds it to |deferred_tasks_queue_|.
   void QueueDeferredTask(const tracked_objects::Location& from_here,
-                         const Closure& task,
+                         Closure task,
                          TimeDelta delay,
                          bool is_non_nestable);
 
   // // Protects |started_| and |deferred_tasks_queue_|.
   mutable Lock lock_;
 
   bool started_;
   const scoped_refptr<SequencedTaskRunner> target_task_runner_;
   std::vector<DeferredTask> deferred_tasks_queue_;
 
   DISALLOW_COPY_AND_ASSIGN(DeferredSequencedTaskRunner);
 };
 
 }  // namespace base
 
 #endif  // BASE_DEFERRED_SEQUENCED_TASK_RUNNER_H_