Replace base::Callback with base::OnceCallback in base::PendingTask

base/task_scheduler/task_tracker.h

 // Copyright 2016 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_SCHEDULER_TASK_TRACKER_H_
 #define BASE_TASK_SCHEDULER_TASK_TRACKER_H_
 
 #include <memory>
 
 #include "base/atomicops.h"
@@ skipping 38 matching lines @@
   // other threads during the call. Returns immediately when shutdown completes.
   void Flush();
 
   // Informs this TaskTracker that |task| is about to be posted. Returns true if
   // this operation is allowed (|task| should be posted if-and-only-if it is).
   bool WillPostTask(const Task* task);
 
   // Runs |task| unless the current shutdown state prevents that.
   // |sequence_token| is the token identifying the sequence from which |task|
   // was extracted. Returns true if |task| ran. WillPostTask() must have allowed
   // |task| to be posted before this is called.

[fdoray, 2016/10/06 17:37:22]

// |task| is non-const to allow running its OnceClosure. It will not be mutated
in other ways.

[tzik, 2016/10/13 05:58:04]

It's now obsolete after your CL, right?
Its type is now std::unique_ptr<Task>, and now it's clear that RunTask retains
the ownership.

-  bool RunTask(const Task* task, const SequenceToken& sequence_token);
+  bool RunTask(Task* task, const SequenceToken& sequence_token);
 
   // Returns true once shutdown has started (Shutdown() has been called but
   // might not have returned). Note: sequential consistency with the thread
   // calling Shutdown() (or SetHasShutdownStartedForTesting()) isn't guaranteed
   // by this call.
   bool HasShutdownStarted() const;
 
   // Returns true if shutdown has completed (Shutdown() has returned).
   bool IsShutdownComplete() const;
 
@@ skipping 60 matching lines @@
   // Number of BLOCK_SHUTDOWN tasks posted during shutdown.
   HistogramBase::Sample num_block_shutdown_tasks_posted_during_shutdown_ = 0;
 
   DISALLOW_COPY_AND_ASSIGN(TaskTracker);
 };
 
 }  // namespace internal
 }  // namespace base
 
 #endif  // BASE_TASK_SCHEDULER_TASK_TRACKER_H_