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

third_party/WebKit/Source/platform/scheduler/base/task_queue_impl.h

 // Copyright 2015 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 THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_IMPL_H_
 #define THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_IMPL_H_
 
 #include <stddef.h>
 
 #include <memory>
 #include <set>
 
+#include "base/callback.h"
 #include "base/macros.h"
 #include "base/pending_task.h"
 #include "base/threading/thread_checker.h"
 #include "base/trace_event/trace_event.h"
 #include "base/trace_event/trace_event_argument.h"
 #include "platform/scheduler/base/enqueue_order.h"
 #include "platform/scheduler/base/intrusive_heap.h"
 #include "public/platform/scheduler/base/task_queue.h"
 #include "wtf/Deque.h"
 
@@ skipping 38 matching lines @@
   TaskQueueImpl(TaskQueueManager* task_queue_manager,
                 TimeDomain* time_domain,
                 const Spec& spec,
                 const char* disabled_by_default_tracing_category,
                 const char* disabled_by_default_verbose_tracing_category);
 
   class BLINK_PLATFORM_EXPORT Task : public base::PendingTask {
    public:
     Task();
     Task(const tracked_objects::Location& posted_from,
-         const base::Closure& task,
+         base::Closure task,
          base::TimeTicks desired_run_time,
          EnqueueOrder sequence_number,
          bool nestable);
 
     Task(const tracked_objects::Location& posted_from,
-         const base::Closure& task,
+         base::Closure task,
          base::TimeTicks desired_run_time,
          EnqueueOrder sequence_number,
          bool nestable,
          EnqueueOrder enqueue_order);
 
     EnqueueOrder enqueue_order() const {
 #ifndef NDEBUG
       DCHECK(enqueue_order_set_);
 #endif
       return enqueue_order_;
@@ skipping 35 matching lines @@
         return (sequence_num - other.sequence_num) < 0;
       }
       return time < other.time;
     }
   };
 
   // TaskQueue implementation.
   void UnregisterTaskQueue() override;
   bool RunsTasksOnCurrentThread() const override;
   bool PostDelayedTask(const tracked_objects::Location& from_here,
-                       const base::Closure& task,
+                       base::Closure task,
                        base::TimeDelta delay) override;
   bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
-                                  const base::Closure& task,
+                                  base::Closure task,
                                   base::TimeDelta delay) override;
   std::unique_ptr<QueueEnabledVoter> CreateQueueEnabledVoter() override;
   bool IsQueueEnabled() const override;
   bool IsEmpty() const override;
   size_t GetNumberOfPendingTasks() const override;
   bool HasPendingImmediateWork() const override;
   base::Optional<base::TimeTicks> GetNextScheduledWakeUp() override;
   void SetQueuePriority(QueuePriority priority) override;
   QueuePriority GetQueuePriority() const override;
   void AddTaskObserver(base::MessageLoop::TaskObserver* task_observer) override;
@@ skipping 130 matching lines @@
     int is_enabled_refcount;
     int voter_refcount;
     base::trace_event::BlameContext* blame_context;  // Not owned.
     EnqueueOrder current_fence;
     base::TimeTicks scheduled_time_domain_wakeup;
   };
 
   ~TaskQueueImpl() override;
 
   bool PostImmediateTaskImpl(const tracked_objects::Location& from_here,
-                             const base::Closure& task,
+                             base::Closure task,
                              TaskType task_type);
   bool PostDelayedTaskImpl(const tracked_objects::Location& from_here,
-                           const base::Closure& task,
+                           base::Closure task,
                            base::TimeDelta delay,
                            TaskType task_type);
 
   // Push the task onto the |delayed_incoming_queue|. Lock-free main thread
   // only fast path.
   void PushOntoDelayedIncomingQueueFromMainThread(Task pending_task,
                                                   base::TimeTicks now);
 
   // Push the task onto the |delayed_incoming_queue|.  Slow path from other
   // threads.
   void PushOntoDelayedIncomingQueueLocked(Task pending_task);
 
   void ScheduleDelayedWorkTask(Task pending_task);
 
   void MoveReadyImmediateTasksToImmediateWorkQueueLocked();
 
   // Push the task onto the |immediate_incoming_queue| and for auto pumped
   // queues it calls MaybePostDoWorkOnMainRunner if the Incoming queue was
   // empty.
   void PushOntoImmediateIncomingQueueLocked(
       const tracked_objects::Location& posted_from,
-      const base::Closure& task,
+      base::Closure task,
       base::TimeTicks desired_run_time,
       EnqueueOrder sequence_number,
       bool nestable);
 
   // Extracts all the tasks from the immediate incoming queue and clears it.
   // Can be called from any thread.
   WTF::Deque<TaskQueueImpl::Task> TakeImmediateIncomingQueue();
 
   void TraceQueueSize(bool is_locked) const;
   static void QueueAsValueInto(const WTF::Deque<Task>& queue,
@@ skipping 41 matching lines @@
   const bool should_report_when_execution_blocked_;
 
   DISALLOW_COPY_AND_ASSIGN(TaskQueueImpl);
 };
 
 }  // namespace internal
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_SOURCE_PLATFORM_SCHEDULER_BASE_TASK_QUEUE_IMPL_H_