Make PendingTask move-only and pass it by value on retaining params

base/message_loop/message_loop.h

 // Copyright 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_MESSAGE_LOOP_MESSAGE_LOOP_H_
 #define BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_
 
 #include <memory>
 #include <queue>
 #include <string>
@@ skipping 432 matching lines @@
   void SetThreadTaskRunnerHandle();
 
   // Invokes the actual run loop using the message pump.
   void RunHandler();
 
   // Called to process any delayed non-nestable tasks.
   bool ProcessNextDelayedNonNestableTask();
 
   // Calls RunTask or queues the pending_task on the deferred task list if it
   // cannot be run right now.  Returns true if the task was run.
-  bool DeferOrRunPendingTask(const PendingTask& pending_task);
+  bool DeferOrRunPendingTask(PendingTask pending_task);
 
   // Adds the pending task to delayed_work_queue_.
-  void AddToDelayedWorkQueue(const PendingTask& pending_task);
+  void AddToDelayedWorkQueue(PendingTask pending_task);
 
   // Delete tasks that haven't run yet without running them.  Used in the
   // destructor to make sure all the task's destructors get called.  Returns
   // true if some work was done.
   bool DeletePendingTasks();
 
   // Loads tasks from the incoming queue to |work_queue_| if the latter is
   // empty.
   void ReloadWorkQueue();
 
@@ skipping 223 matching lines @@
 
 // Do not add any member variables to MessageLoopForIO!  This is important b/c
 // MessageLoopForIO is often allocated via MessageLoop(TYPE_IO).  Any extra
 // data that you need should be stored on the MessageLoop's pump_ instance.
 static_assert(sizeof(MessageLoop) == sizeof(MessageLoopForIO),
               "MessageLoopForIO should not have extra member variables");
 
 }  // namespace base
 
 #endif  // BASE_MESSAGE_LOOP_MESSAGE_LOOP_H_