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

base/bind.cc

Index: base/bind.cc
diff --git a/base/bind.cc b/base/bind.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0fe6ff38e0687fbb6856368c8208ce0958c02c6c
--- /dev/null
+++ b/base/bind.cc
@@ -0,0 +1,15 @@
+// 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.
+
+#include "base/bind.h"
+
+namespace base {
+
+internal::RepeatingClosure UnsafeConvertOnceClosureToRepeating(
+    internal::OnceClosure cb) {
+  return internal::BindRepeating(
+      [](internal::OnceClosure cb) { std::move(cb).Run(); }, Passed(&cb));
+}
+
+}  // namespace base