Add UMA to report Preferences File Corruption

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/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"
 
+class PrefRegistrySimple;
+
 // PrefMetricsService is responsible for recording prefs-related UMA stats.
 class PrefMetricsService : public BrowserContextKeyedService {
  public:
   explicit PrefMetricsService(Profile* profile);
+  // 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);
+
   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:
-  // Use a map to convert domains to their histogram identifiers. Ids are
-  // defined in tools/metrics/histograms/histograms.xml and (usually) also in
-  // chrome/browser/search_engines/prepopulated_engines.json.
-  typedef std::map<std::string, int> DomainIdMap;
+  friend class PrefMetricsServiceTest;
 
   // Function to log a Value to a histogram
   typedef base::Callback<void(const std::string&, const Value*)>
       LogHistogramValueCallback;
 
   // Record prefs state on browser context creation.
   void RecordLaunchPrefs();
 
   // Register callbacks for synced pref changes.
   void RegisterSyncedPrefObservers();
@@ skipping 17 matching lines @@
   void LogIntegerPrefChange(int boundary_value,
                             const std::string& histogram_name,
                             const Value* value);
 
   // Callback for a list pref change. Each item in the list
   // is logged using the given histogram callback.
   void LogListPrefChange(const LogHistogramValueCallback& item_callback,
                          const std::string& histogram_name,
                          const Value* value);
 
+  // Callback to receive a unique device_id. This is used to make it harder to
+  // spoof the preference value checks.
+  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);
+
+  // Removes the tracked preference from local state. Returns 'true' iff. the
+  // value was present.
+  bool RemoveTrackedPreference(const char* path);
+
+  // Gets the path to the preference value hash in local state.
+  std::string GetHashedPrefPath(const char* path);
+
+  // Computes an MD5 hash for the given preference value. Salts the hash with
+  // the pref name and the device id to make it harder to spoof.
+  std::string GetHashedPrefValue(const char* path, const base::Value* value);
+
+  void InitializePrefObservers();
+
+  base::WeakPtrFactory<PrefMetricsService> weak_factory_;
+
   Profile* profile_;
+  PrefService* prefs_;
+  PrefService* local_state_;
+  std::string profile_name_;
+  std::string device_id_;
+  const char** tracked_pref_paths_;
+  const int tracked_pref_path_count_;
+
+  PrefChangeRegistrar pref_registrar_;
   scoped_ptr<SyncedPrefChangeRegistrar> synced_pref_change_registrar_;
 };
 
 #endif  // CHROME_BROWSER_PREFS_PREF_METRICS_SERVICE_H_