1// Copyright 2014 The Chromium Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef COMPONENTS_METRICS_CLEAN_EXIT_BEACON_H_
6#define COMPONENTS_METRICS_CLEAN_EXIT_BEACON_H_
7
8#include "base/macros.h"
9#include "base/strings/string16.h"
10
11class PrefService;
12
13namespace metrics {
14
15// Reads and updates a beacon used to detect whether the previous browser
16// process exited cleanly.
17class CleanExitBeacon {
18 public:
19  // Instantiates a CleanExitBeacon whose value is stored in |local_state|.
20  // |local_state| must be fully initialized.
21  // On Windows, |backup_registry_key| is used to store a backup of the beacon.
22  // It is ignored on other platforms.
23  CleanExitBeacon(
24      const base::string16& backup_registry_key,
25      PrefService* local_state);
26
27  ~CleanExitBeacon();
28
29  // Returns the original value of the beacon.
30  bool exited_cleanly() const { return initial_value_; }
31
32  // Writes the provided beacon value.
33  void WriteBeaconValue(bool exited_cleanly);
34
35 private:
36  PrefService* const local_state_;
37  const bool initial_value_;
38  const base::string16 backup_registry_key_;
39
40  DISALLOW_COPY_AND_ASSIGN(CleanExitBeacon);
41};
42
43}  // namespace metrics
44
45#endif  // COMPONENTS_METRICS_CLEAN_EXIT_BEACON_H_
46