Delete the PreferenceMACs on profile deletion.

components/prefs/pref_service.cc

 // 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.
 
 #include "components/prefs/pref_service.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 356 matching lines @@
     NOTREACHED() << "Trying to clear an unregistered pref: " << path;
     return;
   }
   user_pref_store_->RemoveValue(path, GetWriteFlags(pref));
 }
 
 void PrefService::ClearMutableValues() {
   user_pref_store_->ClearMutableValues();
 }
 
+void PrefService::OnStoreDeletionFromDisk() {
+  user_pref_store_->OnStoreDeletionFromDisk();
+}
+
 void PrefService::Set(const std::string& path, const base::Value& value) {
   SetUserPrefValue(path, value.CreateDeepCopy());
 }
 
 void PrefService::SetBoolean(const std::string& path, bool value) {
   SetUserPrefValue(path, base::MakeUnique<base::Value>(value));
 }
 
 void PrefService::SetInteger(const std::string& path, int value) {
   SetUserPrefValue(path, base::MakeUnique<base::Value>(value));
@@ skipping 226 matching lines @@
       DCHECK(found_value->IsType(default_type));
       return found_value;
     } else {
       // Every registered preference has at least a default value.
       NOTREACHED() << "no valid value found for registered pref " << path;
     }
   }
 
   return NULL;
 }