Revert of Pref service: add support for tracked prefs.

services/preferences/persistent_pref_store_impl_unittest.cc

Index: services/preferences/persistent_pref_store_impl_unittest.cc
diff --git a/services/preferences/persistent_pref_store_impl_unittest.cc b/services/preferences/persistent_pref_store_impl_unittest.cc
index 7a326276c0a76ff2b8fe5ad258de217afdf93bc7..60fa2ffcb91bad3ad609f58c2124832970453867 100644
--- a/services/preferences/persistent_pref_store_impl_unittest.cc
+++ b/services/preferences/persistent_pref_store_impl_unittest.cc
@@ -119,7 +119,7 @@
     base::RunLoop run_loop;
     bool initialized = backing_pref_store->IsInitializationComplete();
     impl_ = base::MakeUnique<PersistentPrefStoreImpl>(
-        std::move(backing_pref_store), run_loop.QuitClosure());
+        std::move(backing_pref_store), nullptr, run_loop.QuitClosure());
     if (!initialized)
       run_loop.Run();
     pref_store_ = CreateConnection();