Introduce PrefRegistrySyncable, simplifying PrefServiceSyncable.

chrome/browser/prefs/pref_service_mock_builder.cc

Index: chrome/browser/prefs/pref_service_mock_builder.cc
diff --git a/chrome/browser/prefs/pref_service_mock_builder.cc b/chrome/browser/prefs/pref_service_mock_builder.cc
index dc2803cb982c6373fe487734d5cd5865af33b0d0..51ae6fb8e11c9c6001d3a6dd8e2c1aafa336cb47 100644
--- a/chrome/browser/prefs/pref_service_mock_builder.cc
+++ b/chrome/browser/prefs/pref_service_mock_builder.cc
@@ -5,6 +5,7 @@
 #include "chrome/browser/prefs/pref_service_mock_builder.h"
 
 #include "base/prefs/testing_pref_store.h"
+#include "chrome/browser/prefs/pref_registry_syncable.h"
 
 PrefServiceMockBuilder::PrefServiceMockBuilder() {
   ResetDefaultState();
@@ -17,8 +18,10 @@ PrefService* PrefServiceMockBuilder::Create(PrefRegistry* pref_registry) {
   return service;
 }
 
-PrefServiceSyncable* PrefServiceMockBuilder::CreateSyncable() {
-  PrefServiceSyncable* service = PrefServiceSyncableBuilder::CreateSyncable();
+PrefServiceSyncable* PrefServiceMockBuilder::CreateSyncable(
+    PrefRegistrySyncable* pref_registry) {
+  PrefServiceSyncable* service =
+      PrefServiceSyncableBuilder::CreateSyncable(pref_registry);
   return service;
 }