Delete the PreferenceMACs on profile deletion.

components/prefs/json_pref_store.h

 // Copyright (c) 2012 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_PREFS_JSON_PREF_STORE_H_
 #define COMPONENTS_PREFS_JSON_PREF_STORE_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 100 matching lines @@
 
   // Registers |on_next_successful_write_reply| to be called once, on the next
   // successful write event of |writer_|.
   // |on_next_successful_write_reply| will be called on the thread from which
   // this method is called and does not need to be thread safe.
   void RegisterOnNextSuccessfulWriteReply(
       const base::Closure& on_next_successful_write_reply);
 
   void ClearMutableValues() override;
 
+  void OnStoreDeletionFromDisk() override;
+
  private:
   // Represents a histogram for recording the number of writes to the pref file
   // that occur every kHistogramWriteReportIntervalInMins minutes.
   class COMPONENTS_PREFS_EXPORT WriteCountHistogram {
    public:
     static const int32_t kHistogramWriteReportIntervalMins;
 
     WriteCountHistogram(const base::TimeDelta& commit_interval,
                         const base::FilePath& path);
     // Constructor for testing. |clock| is a test Clock that is used to retrieve
@@ skipping 120 matching lines @@
   base::Closure on_next_successful_write_reply_;
 
   WriteCountHistogram write_count_histogram_;
 
   SEQUENCE_CHECKER(sequence_checker_);
 
   DISALLOW_COPY_AND_ASSIGN(JsonPrefStore);
 };
 
 #endif  // COMPONENTS_PREFS_JSON_PREF_STORE_H_