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

base/bind.h

 // Copyright (c) 2011 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_BIND_H_
 #define BASE_BIND_H_
 
 #include "base/bind_internal.h"
 
 // -----------------------------------------------------------------------------
@@ skipping 63 matching lines @@
 // Unannotated Bind.
 // TODO(tzik): Deprecate this and migrate to OnceCallback and
 // RepeatingCallback, once they get ready.
 template <typename Functor, typename... Args>
 inline Callback<MakeUnboundRunType<Functor, Args...>>
 Bind(Functor&& functor, Args&&... args) {
   return internal::BindRepeating(std::forward<Functor>(functor),
                                  std::forward<Args>(args)...);
 }
 
+// Converts a OnceClosure to a RepeatingClosure. It hits CHECK failure to run
+// the resulting RepeatingClosure more than once.
+BASE_EXPORT internal::RepeatingClosure UnsafeConvertOnceClosureToRepeating(

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

Do you plan to use OnceClosure instead of Closure in TaskRunner? I would be in
favor of that change.

If so, add a TODO to remove this function once TaskRunner uses OnceClosure
(third_party/WebKit/Source/platform/scheduler/base/task_queue_manager.cc will no
longer need this conversion)

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

Yes, here is a CL to do that, though it's a bit stale now.
https://codereview.chromium.org/2122543002/
Done.

+    internal::OnceClosure cb);
+
 }  // namespace base
 
 #endif  // BASE_BIND_H_