Add APIs to protect critical tasks on iOS.

base/critical_closure_ios.mm

Index: base/critical_closure_ios.mm
diff --git a/base/critical_closure_ios.mm b/base/critical_closure_ios.mm
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+// 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) {
+    background_scope_.reset(new base::ios::ScopedCriticalAction());
+  }
+
+  void Run() {
+    closure_->Run();
+
+    background_scope_.reset();
+  }
+
+ private:
+  friend class base::RefCountedThreadSafe<CriticalClosure>;
+
+  virtual ~CriticalClosure() {}
+
+  scoped_ptr<base::Closure> closure_;
+  scoped_ptr<base::ios::ScopedCriticalAction> background_scope_;
+
+  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