Introduce a new framework for back-and-forth tracked/protected preferences migration.

base/critical_closure_ios.mm

-// 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.
-
-#include "base/critical_closure.h"
-
-#import <UIKit/UIKit.h>
-
-#include "base/bind.h"
-#include "base/ios/scoped_critical_action.h"
-#include "base/memory/ref_counted.h"
-
-namespace {
-
-// This class wraps a closure so it can continue to run for a period of time
-// when the application goes to the background by using
-// |base::ios::ScopedCriticalAction|.
-class CriticalClosure : public base::RefCountedThreadSafe<CriticalClosure> {
- public:
-  explicit CriticalClosure(base::Closure* closure) : closure_(closure) {
-  }
-
-  void Run() {
-    closure_->Run();
-  }
-
- private:
-  friend class base::RefCountedThreadSafe<CriticalClosure>;
-
-  virtual ~CriticalClosure() {}
-
-  base::ios::ScopedCriticalAction criticial_action_;
-  scoped_ptr<base::Closure> closure_;
-
-  DISALLOW_COPY_AND_ASSIGN(CriticalClosure);
-};
-
-}  // namespace
-
-namespace base {
-
-base::Closure MakeCriticalClosure(const base::Closure& closure) {
-  DCHECK([[UIDevice currentDevice] isMultitaskingSupported]);
-  scoped_refptr<CriticalClosure> critical_closure(
-      new CriticalClosure(new base::Closure(closure)));
-  return base::Bind(&CriticalClosure::Run, critical_closure.get());
-}
-
-}  // namespace base