Fix a race condition in preference metric reporting.

chrome/browser/prefs/pref_metrics_service.h

 // Copyright 2013 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_PREFS_PREF_METRICS_SERVICE_H_
 #define CHROME_BROWSER_PREFS_PREF_METRICS_SERVICE_H_
 
 #include <map>
 #include <string>
 
+#include "base/basictypes.h"
+#include "base/callback.h"
+#include "base/compiler_specific.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/memory/singleton.h"
 #include "base/memory/weak_ptr.h"
 #include "base/prefs/pref_change_registrar.h"
 #include "chrome/browser/prefs/synced_pref_change_registrar.h"
-#include "chrome/browser/profiles/profile.h"
 #include "components/browser_context_keyed_service/browser_context_keyed_service.h"
 #include "components/browser_context_keyed_service/browser_context_keyed_service_factory.h"
 
+namespace base {
+class Value;
+}  // namespace base
+
+namespace content {
+class BrowserContext;
+}  // namespace content
+
+class Profile;
 class PrefRegistrySimple;
+class PrefService;
 
 // PrefMetricsService is responsible for recording prefs-related UMA stats.
 class PrefMetricsService : public BrowserContextKeyedService {
  public:
-  enum HashedPrefStyle {
-    HASHED_PREF_STYLE_NEW,
-    HASHED_PREF_STYLE_DEPRECATED,
-  };
-
   explicit PrefMetricsService(Profile* profile);
   virtual ~PrefMetricsService();
 
   class Factory : public BrowserContextKeyedServiceFactory {
    public:
     static Factory* GetInstance();
     static PrefMetricsService* GetForProfile(Profile* profile);
    private:
     friend struct DefaultSingletonTraits<Factory>;
 
     Factory();
     virtual ~Factory();
 
     // BrowserContextKeyedServiceFactory implementation
     virtual BrowserContextKeyedService* BuildServiceInstanceFor(
         content::BrowserContext* profile) const OVERRIDE;
     virtual bool ServiceIsCreatedWithBrowserContext() const OVERRIDE;
     virtual bool ServiceIsNULLWhileTesting() const OVERRIDE;
     virtual content::BrowserContext* GetBrowserContextToUse(
         content::BrowserContext* context) const OVERRIDE;
   };
 
   // Registers preferences in local state.
   static void RegisterPrefs(PrefRegistrySimple* registry);
 
  private:
   friend class PrefMetricsServiceTest;
 
   // Function to log a Value to a histogram
-  typedef base::Callback<void(const std::string&, const Value*)>
+  typedef base::Callback<void(const std::string&, const base::Value*)>
       LogHistogramValueCallback;
 
   // For unit testing only.
-  PrefMetricsService(Profile* profile,
-                     PrefService* local_settings,
-                     const std::string& device_id,
-                     const char** tracked_pref_paths,
-                     int tracked_pref_path_count);
+  PrefMetricsService(Profile* profile, PrefService* local_settings);
 
   // Record prefs state on browser context creation.
   void RecordLaunchPrefs();
 
   // Register callbacks for synced pref changes.
   void RegisterSyncedPrefObservers();
 
   // Registers a histogram logging callback for a synced pref change.
   void AddPrefObserver(const std::string& path,
                        const std::string& histogram_name_prefix,
                        const LogHistogramValueCallback& callback);
 
   // Generic callback to observe a synced pref change.
   void OnPrefChanged(const std::string& histogram_name_prefix,
                      const LogHistogramValueCallback& callback,
                      const std::string& path,
                      bool from_sync);
 
   // Callback for a boolean pref change histogram.
   void LogBooleanPrefChange(const std::string& histogram_name,
-                            const Value* value);
+                            const base::Value* value);
 
   // Callback for an integer pref change histogram.
   void LogIntegerPrefChange(int boundary_value,
                             const std::string& histogram_name,
-                            const Value* value);
-
-  // Callback to receive a unique device_id.
-  void GetDeviceIdCallback(const std::string& device_id);
-
-  // Checks the tracked preferences against their last known values and reports
-  // any discrepancies. This must be called after |device_id| has been set.
-  void CheckTrackedPreferences();
-
-  // Updates the hash of the tracked preference in local state. This must be
-  // called after |device_id| has been set.
-  void UpdateTrackedPreference(const char* path);
-
-  // Computes an MD5 hash for the given preference value. |value| can be
-  // NULL which will result in the unique hash representing NULL for the pref
-  // at |path|.
-  std::string GetHashedPrefValue(
-      const char* path,
-      const base::Value* value,
-      HashedPrefStyle desired_style);
-
-  void InitializePrefObservers();
+                            const base::Value* value);
 
   Profile* profile_;
   PrefService* prefs_;
   PrefService* local_state_;
-  std::string profile_name_;
-  std::string pref_hash_seed_;
-  std::string device_id_;
-  const char** tracked_pref_paths_;
-  const int tracked_pref_path_count_;
-  bool checked_tracked_prefs_;
 
   PrefChangeRegistrar pref_registrar_;
   scoped_ptr<SyncedPrefChangeRegistrar> synced_pref_change_registrar_;
 
   base::WeakPtrFactory<PrefMetricsService> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PrefMetricsService);
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_METRICS_SERVICE_H_