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 60 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 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.
+// TODO(tzik): This will be unneeded after the Closure-to-OnceClosure migration
+// on TaskRunner. Remove it once it gets unneeded.
+BASE_EXPORT RepeatingClosure UnsafeConvertOnceClosureToRepeating(
+    OnceClosure cb);
+
 }  // namespace base
 
 #endif  // BASE_BIND_H_