Pref service: integrate PersistentPrefStoreImpl with PrefStoreManagerImpl.

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/values.mojom";
+import "services/preferences/public/interfaces/preferences_configuration.mojom";
 
 const string kServiceName = "preferences";
 
 // Used for the creation of a PreferencesService and to ensure that the
 // PreferencesServiceClient is bound at creation time.
 interface PreferencesServiceFactory {
   // Creates a PreferencesService bound to the provided |observer|.
   Create(PreferencesServiceClient observer, PreferencesService& service);
 };
 
@@ skipping 107 matching lines @@
   // |pref_store| provides write access; |observer| is used to observe writes
   // instigated by other clients.
   [Sync]
   Connect() => (
       ReadError read_error,
       bool read_only,
       mojo.common.mojom.DictionaryValue? preferences,
       PersistentPrefStore? pref_store,
       PrefStoreObserver&? observer);
 };
+
+interface PrefServiceControl {
+  // Initializes the pref service. This must be called before the service can
+  // be used.
+  Init(PersistentPrefStoreConfiguration configuration);
+};