Retrieve client_id from GoogleUpdateSettings when its missing from Local State.

components/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 COMPONENTS_METRICS_METRICS_STATE_MANAGER_H_
 #define COMPONENTS_METRICS_METRICS_STATE_MANAGER_H_
 
 #include <string>
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/gtest_prod_util.h"
+#include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/metrics/field_trial.h"
+#include "components/metrics/client_info.h"
 
 class PrefService;
 class PrefRegistrySimple;
 
 namespace metrics {
 
 class ClonedInstallDetector;
 
 // Responsible for managing MetricsService state prefs, specifically the UMA
 // client id and low entropy source. Code outside the metrics directory should
 // not be instantiating or using this class directly.
 class MetricsStateManager {
  public:
+  // A callback that can be invoked to store client info to persistent storage.
+  // Storing an empty client_id will resulted in the backup being voided.
+  typedef base::Callback<void(const ClientInfo& client_info)>
+      StoreClientInfoCallback;
+
+  // A callback that can be invoked to load client info stored through the
+  // StoreClientInfoCallback.
+  typedef base::Callback<scoped_ptr<ClientInfo>(void)> LoadClientInfoCallback;
+
   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_; }
 
   // Forces the client ID to be generated. This is useful in case it's needed
@@ skipping 12 matching lines @@
   // If metrics reporting is enabled, this method returns an entropy provider
   // that has a high source of entropy, partially based on the client ID.
   // Otherwise, it returns an entropy provider that is based on a low entropy
   // source.
   scoped_ptr<const base::FieldTrial::EntropyProvider> CreateEntropyProvider();
 
   // Creates the MetricsStateManager, enforcing that only a single instance
   // of the class exists at a time. Returns NULL if an instance exists already.
   static scoped_ptr<MetricsStateManager> Create(
       PrefService* local_state,
-      const base::Callback<bool(void)>& is_reporting_enabled_callback);
+      const base::Callback<bool(void)>& is_reporting_enabled_callback,
+      const StoreClientInfoCallback& store_client_info,
+      const LoadClientInfoCallback& load_client_info);
 
   // 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 class.
   // This is used for testing to validate that we return the correct source
   // depending on the state of the service.
   enum EntropySourceType {
     ENTROPY_SOURCE_NONE,
     ENTROPY_SOURCE_LOW,
     ENTROPY_SOURCE_HIGH,
   };
 
   // Creates the MetricsStateManager with the given |local_state|. Calls
   // |is_reporting_enabled_callback| to query whether metrics reporting is
-  // enabled. Clients should instead use Create(), which enforces a single
-  // instance of this class is alive at any given time.
+  // enabled. Clients should instead use Create(), which enforces that a single
+  // instance of this class be alive at any given time.
+  // |store_client_info| should back up client info to persistent storage such
+  // that it is later retrievable by |load_client_info|.
   MetricsStateManager(
       PrefService* local_state,
-      const base::Callback<bool(void)>& is_reporting_enabled_callback);
+      const base::Callback<bool(void)>& is_reporting_enabled_callback,
+      const StoreClientInfoCallback& store_client_info,
+      const LoadClientInfoCallback& load_client_info);
+
+  // Backs up the current client info via |store_client_info_|.
+  void BackUpCurrentClientInfo();
+
+  // Loads the client info via |load_client_info_| and potentially migrates it
+  // before returning it if it comes back in its old form.
+  scoped_ptr<ClientInfo> LoadClientInfoAndMaybeMigrate();
 
   // 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.
   EntropySourceType entropy_source_returned() const {
     return entropy_source_returned_;
   }
 
   // Reset the client id and low entropy source if the kMetricsResetMetricIDs
   // pref is true.
   void ResetMetricsIDsIfNecessary();
 
   // Whether an instance of this class exists. Used to enforce that there aren't
   // multiple instances of this class at a given time.
   static bool instance_exists_;
 
   // Weak pointer to the local state prefs store.
   PrefService* const local_state_;
 
+  // A callback run by this MetricsStateManager to know whether reporting is
+  // enabled.
   const base::Callback<bool(void)> is_reporting_enabled_callback_;
 
+  // A callback run during client id creation so this MetricsStateManager can
+  // store a backup of the newly generated ID.
+  const StoreClientInfoCallback store_client_info_;
+
+  // A callback run if this MetricsStateManager can't get the client id from
+  // its typical location and wants to attempt loading it from this backup.
+  const LoadClientInfoCallback load_client_info_;
+
   // 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.
   EntropySourceType entropy_source_returned_;
 
   scoped_ptr<ClonedInstallDetector> cloned_install_detector_;
 
   DISALLOW_COPY_AND_ASSIGN(MetricsStateManager);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_METRICS_STATE_MANAGER_H_