Delete the PreferenceMACs on profile deletion.

services/preferences/persistent_pref_store_impl.h

 // Copyright 2017 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 SERVICES_PREFERENCES_PERSISTENT_PREF_STORE_IMPL_H_
 #define SERVICES_PREFERENCES_PERSISTENT_PREF_STORE_IMPL_H_
 
 #include <memory>
 #include <string>
 #include <unordered_map>
@@ skipping 25 matching lines @@
 
  private:
   class Connection;
 
   void SetValues(std::vector<mojom::PrefUpdatePtr> updates);
   bool GetValue(const std::string& key, const base::Value** value) const;
 
   void CommitPendingWrite(base::OnceClosure done_callback);
   void SchedulePendingLossyWrites();
   void ClearMutableValues();
+  void OnStoreDeletionFromDisk();
 
   // PrefStore::Observer:
   void OnPrefValueChanged(const std::string& key) override;
   void OnInitializationCompleted(bool succeeded) override;
 
   void OnConnectionError(Connection* connection);
 
   scoped_refptr<PersistentPrefStore> backing_pref_store_;
 
   bool initializing_ = false;
 
   std::unordered_map<Connection*, std::unique_ptr<Connection>> connections_;
 
   base::OnceClosure on_initialized_;
 
   DISALLOW_COPY_AND_ASSIGN(PersistentPrefStoreImpl);
 };
 
 }  // namespace prefs
 
 #endif  // SERVICES_PREFERENCES_PERSISTENT_PREF_STORE_IMPL_H_