Add APIs to protect critical tasks on iOS.

base/critical_closure.h

+// Copyright (c) 2012 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_CRITICAL_CLOSURE_H_
+#define BASE_CRITICAL_CLOSURE_H_
+
+#include "base/callback.h"
+
+namespace base {
+
+// Returns a closure that is protected when the application goes to the

[Mark Mentovai, 2012/07/31 23:16:33]

You don’t say what “protected” means, but it’s totally unclear so you should.

[Chen Yu, 2012/08/01 11:26:13]

Done.

+// background (on platforms where applications don't execute while backgrounded)
+// if possible, otherwise the original task is returned.
+//
+// Example:
+//   file_message_loop_proxy_->PostTask(
+//       FROM_HERE,
+//       MakeCriticalClosure(base::Bind(&WriteToDiskTask, path_, data)));
+//
+// Note new closures might be posted in this closure. If the new closures need
+// to be protected, |MakeCriticalClosure| should be applied on them before
+// posting.
+base::Closure MakeCriticalClosure(const base::Closure& closure);
+
+}  // namespace base
+
+#endif  // BASE_CRITICAL_CLOSURE_H_