Refactor MetricsStateManager class out of MetricsService.

chrome/browser/metrics/metrics_state_manager.h

+// 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.
+
+#ifndef CHROME_BROWSER_METRICS_METRICS_STATE_MANAGER_H_
+#define CHROME_BROWSER_METRICS_METRICS_STATE_MANAGER_H_
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/gtest_prod_util.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/metrics/field_trial.h"
+
+class PrefService;
+class PrefRegistrySimple;
+
+namespace metrics {
+
+class ClonedInstallDetector;
+
+// Responsible for managing MetricsService state prefs, specifically the UMA
+// client id and low entropy source.
+class MetricsStateManager {
+ public:
+  explicit MetricsStateManager(PrefService* local_state);
+  virtual ~MetricsStateManager();
+
+  // Returns true if the user opted in to sending metric reports.
+  bool IsMetricsReportingEnabled();
+
+  // Returns the client ID for this client, or the empty string if the user is
+  // not opted in to metrics reporting.
+  const std::string& client_id() const { return client_id_; }
+
+  // Force the client ID to be generated. This is useful in case it's needed
+  // before recording.
+  void ForceClientIdCreation();

[jwd, 2014/05/01 15:51:14]

Is this needed public? Since it's always called on construction.

[Alexei Svitkine (slow), 2014/05/01 18:01:45]

It's public because it's also called from MetricsService::EnableRecording(),
which can be done later than start up (e.g. after the user enables metrics
reporting half-way through a session).

+
+  // Check if this install was cloned or imaged from another machine. If a
+  // clone is detected, reset the client id and low entropy source. This
+  // should not be called more than once.
+  void CheckForClonedInstall();
+
+  // Returns the preferred entropy provider used to seed persistent activities
+  // based on whether or not metrics reporting will be permitted on this client.
+  // The caller must determine if metrics reporting will be enabled for this
+  // client and pass that state in as |reporting_will_be_enabled|.

[jwd, 2014/05/01 15:51:14]

Update comment re: |reporting_will_be_enabled|

[Alexei Svitkine (slow), 2014/05/01 18:01:45]

Done.

+  //
+  // If |reporting_will_be_enabled| is true, this method returns an entropy
+  // provider that has a high source of entropy, partially based on the client
+  // ID. Otherwise, an entropy provider that is based on a low entropy source
+  // is returned.
+  //
+  // Note that this reporting state can not be checked by reporting_active()
+  // because this method may need to be called before the MetricsService needs
+  // to be started.
+  scoped_ptr<const base::FieldTrial::EntropyProvider> CreateEntropyProvider();
+
+  // Registers local state prefs used by this class.
+  static void RegisterPrefs(PrefRegistrySimple* registry);
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, EntropySourceUsed_Low);
+  FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, EntropySourceUsed_High);
+  FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, LowEntropySource0NotReset);
+  FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest,
+                           PermutedEntropyCacheClearedWhenLowEntropyReset);
+  FRIEND_TEST_ALL_PREFIXES(MetricsStateManagerTest, ResetMetricsIDs);
+
+  // Designates which entropy source was returned from this MetricsService.
+  // This is used for testing to validate that we return the correct source
+  // depending on the state of the service.
+  enum EntropySourceReturned {
+    LAST_ENTROPY_NONE,
+    LAST_ENTROPY_LOW,
+    LAST_ENTROPY_HIGH,
+  };
+
+  // Returns the low entropy source for this client. This is a random value
+  // that is non-identifying amongst browser clients. This method will
+  // generate the entropy source value if it has not been called before.
+  int GetLowEntropySource();
+
+  // Returns the first entropy source that was returned by this service since
+  // start up, or NONE if neither was returned yet. This is exposed for testing
+  // only.
+  EntropySourceReturned entropy_source_returned() const {
+    return entropy_source_returned_;
+  }
+
+  // Reset the client id and low entropy source if the kMetricsResetMetricIDs
+  // pref is true.
+  void ResetMetricsIDsIfNecessary();
+
+  PrefService* local_state_;
+
+  // TODO(asvitkine): Update this when the user toggles this state.
+  bool metrics_reporting_enabled_;
+
+  // The identifier that's sent to the server with the log reports.
+  std::string client_id_;
+
+  // The non-identifying low entropy source value.
+  int low_entropy_source_;
+
+  // The last entropy source returned by this service, used for testing.
+  EntropySourceReturned entropy_source_returned_;
+
+  // Set to true when |ResetMetricsIDsIfNecessary| is called for the first time.
+  // This prevents multiple resets within the same Chrome session.
+  bool metrics_ids_reset_check_performed_;
+
+  scoped_ptr<ClonedInstallDetector> cloned_install_detector_;
+
+  DISALLOW_COPY_AND_ASSIGN(MetricsStateManager);
+};
+
+}  // namespace metrics
+
+#endif  // CHROME_BROWSER_METRICS_METRICS_STATE_MANAGER_H_