Delete the PreferenceMACs on profile deletion.

services/preferences/public/interfaces/preferences.mojom

 // Copyright 2016 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.
 
 module prefs.mojom;
 
 import "mojo/common/file_path.mojom";
 import "mojo/common/string16.mojom";
 import "mojo/common/values.mojom";
 import "services/preferences/public/interfaces/tracked_preference_validation_delegate.mojom";
@@ skipping 131 matching lines @@
 
 // An interface providing mutation access to a PersistentPrefStore.
 interface PersistentPrefStore {
   // Sets the values for prefs.
   SetValues(array<PrefUpdate> updates);
 
   // These mirror the C++ PersistentPrefStore methods.
   CommitPendingWrite();
   SchedulePendingLossyWrites();
   ClearMutableValues();
+  OnStoreDeletionFromDisk();
 };
 
 // A registry of all prefs registered by a single client.
 struct PrefRegistry {
   array<string> registrations;
 };
 
 struct PrefRegistration {
   mojo.common.mojom.Value default_value;
 
@@ skipping 63 matching lines @@
 };
 
 interface ResetOnLoadObserver {
   OnResetOnLoad();
 };
 
 struct IncognitoPersistentPrefStoreConfiguration {
   // A connector for the underlying profile's prefs.
   PrefStoreConnector connector;
 };