Add APIs to protect critical tasks on iOS.

base/critical_closure.h

Index: base/critical_closure.h
diff --git a/base/critical_closure.h b/base/critical_closure.h
new file mode 100644
index 0000000000000000000000000000000000000000..e0e24d47bfa4bd3c647dd43138ca227627dcd0e8
--- /dev/null
+++ b/base/critical_closure.h
@@ -0,0 +1,23 @@
+// 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"
+
+// Returns a closure that is protected when the application goes to the
+// background if possible, otherwise the original task is returned.

[stuartmorgan, 2012/07/31 07:58:15]

s/background/background (on platforms where applications don't execute while
backgrounded)/

+//
+// 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);
+
+#endif  // BASE_CRITICAL_CLOSURE_H_