Extract the handling of the clean exit beacon from MetricsService. The extracted implementation sup…

components/metrics/clean_exit_beacon.cc

+// Copyright 2014 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 "components/metrics/clean_exit_beacon.h"
+
+#include "base/logging.h"
+#include "base/prefs/pref_service.h"
+#include "components/metrics/metrics_pref_names.h"
+
+#if defined(OS_WIN)
+#include "base/metrics/histogram.h"
+#include "base/strings/utf_string_conversions.h"
+#include "base/win/registry.h"
+#endif
+
+namespace metrics {
+
+CleanExitBeacon::CleanExitBeacon(const base::string16& backup_registry_key,
+                                 PrefService* local_state)
+    : local_state_(local_state),
+      initial_value_(
+          local_state->GetBoolean(metrics::prefs::kStabilityExitedCleanly)),
+      backup_registry_key_(backup_registry_key) {
+  DCHECK_NE(PrefService::INITIALIZATION_STATUS_WAITING,
+            local_state_->GetInitializationStatus());
+
+#if defined(OS_WIN)
+  // An enumeration of all possible permutations of the the beacon state in the
+  // registry and in Local State.
+  enum {
+    DIRTY_DIRTY,
+    DIRTY_CLEAN,
+    CLEAN_DIRTY,
+    CLEAN_CLEAN,
+    MISSING_DIRTY,
+    MISSING_CLEAN,
+    NUM_CONSISTENCY_ENUMS
+  } consistency = DIRTY_DIRTY;
+
+  base::win::RegKey regkey;
+  DWORD value = 0u;
+  if (regkey.Open(HKEY_CURRENT_USER,
+                  backup_registry_key_.c_str(),
+                  KEY_ALL_ACCESS) == ERROR_SUCCESS &&
+      regkey.ReadValueDW(
+          base::ASCIIToUTF16(metrics::prefs::kStabilityExitedCleanly).c_str(),
+          &value) == ERROR_SUCCESS) {
+    if (value)
+      consistency = initial_value_ ? CLEAN_CLEAN : CLEAN_DIRTY;
+    else
+      consistency = initial_value_ ? DIRTY_CLEAN : DIRTY_DIRTY;
+  } else {
+    consistency = initial_value_ ? MISSING_CLEAN : MISSING_DIRTY;
+  }
+
+  UMA_HISTOGRAM_ENUMERATION(
+      "UMA.CleanExitBeaconConsistency", consistency, NUM_CONSISTENCY_ENUMS);
+#endif
+}
+
+CleanExitBeacon::~CleanExitBeacon() {
+}
+
+void CleanExitBeacon::WriteBeaconValue(bool value) {
+  local_state_->SetBoolean(metrics::prefs::kStabilityExitedCleanly, value);
+
+#if defined(OS_WIN)
+  base::win::RegKey regkey;
+  if (regkey.Create(HKEY_CURRENT_USER,
+                    backup_registry_key_.c_str(),
+                    KEY_ALL_ACCESS) == ERROR_SUCCESS) {
+    regkey.WriteValue(
+        base::ASCIIToUTF16(metrics::prefs::kStabilityExitedCleanly).c_str(),
+        value ? 1u : 0u);
+  }
+#endif
+}
+
+}  // namespace metrics