Standardize usage of virtual/override/final in storage/

storage/browser/quota/usage_tracker.h

Index: storage/browser/quota/usage_tracker.h
diff --git a/storage/browser/quota/usage_tracker.h b/storage/browser/quota/usage_tracker.h
index 02b64de0bb7c05e83d9fbc28238e7f3fa1b932c4..b19aea158543db6e9a97c8444f968090a96fb5e4 100644
--- a/storage/browser/quota/usage_tracker.h
+++ b/storage/browser/quota/usage_tracker.h
@@ -35,7 +35,7 @@ class STORAGE_EXPORT UsageTracker : public QuotaTaskObserver {
   UsageTracker(const QuotaClientList& clients, StorageType type,
                SpecialStoragePolicy* special_storage_policy,
                StorageMonitor* storage_monitor);
-  virtual ~UsageTracker();
+  ~UsageTracker() override;
 
   StorageType type() const { return type_; }
   ClientUsageTracker* GetClientTracker(QuotaClient::ID client_id);
@@ -107,7 +107,7 @@ class ClientUsageTracker : public SpecialStoragePolicy::Observer,
                      StorageType type,
                      SpecialStoragePolicy* special_storage_policy,
                      StorageMonitor* storage_monitor);
-  virtual ~ClientUsageTracker();
+  ~ClientUsageTracker() override;
 
   void GetGlobalLimitedUsage(const UsageCallback& callback);
   void GetGlobalUsage(const GlobalUsageCallback& callback);
@@ -169,9 +169,9 @@ class ClientUsageTracker : public SpecialStoragePolicy::Observer,
   bool GetCachedOriginUsage(const GURL& origin, int64* usage) const;
 
   // SpecialStoragePolicy::Observer overrides
-  virtual void OnGranted(const GURL& origin, int change_flags) override;
-  virtual void OnRevoked(const GURL& origin, int change_flags) override;
-  virtual void OnCleared() override;
+  void OnGranted(const GURL& origin, int change_flags) override;
+  void OnRevoked(const GURL& origin, int change_flags) override;
+  void OnCleared() override;
 
   bool IsStorageUnlimited(const GURL& origin) const;