Pref service: add support for tracked prefs.

services/preferences/persistent_pref_store_impl_unittest.cc

 // Copyright 2017 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 "services/preferences/persistent_pref_store_impl.h"
 
 #include <utility>
 
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
@@ skipping 101 matching lines @@
     pref_store_ = nullptr;
     base::RunLoop().RunUntilIdle();
     impl_.reset();
     base::RunLoop().RunUntilIdle();
   }
 
   void CreateImpl(scoped_refptr<PersistentPrefStore> backing_pref_store) {
     base::RunLoop run_loop;
     bool initialized = backing_pref_store->IsInitializationComplete();
     impl_ = base::MakeUnique<PersistentPrefStoreImpl>(
-        std::move(backing_pref_store), nullptr, run_loop.QuitClosure());
+        std::move(backing_pref_store), run_loop.QuitClosure());
     if (!initialized)
       run_loop.Run();
     pref_store_ = CreateConnection();
   }
 
   scoped_refptr<PersistentPrefStore> CreateConnection(
       PersistentPrefStoreImpl::ObservedPrefs observed_prefs =
           PersistentPrefStoreImpl::ObservedPrefs()) {
     if (observed_prefs.empty())
       observed_prefs.insert({kKey, kOtherKey});
@@ skipping 194 matching lines @@
   base::RunLoop run_loop;
   EXPECT_CALL(*backing_store, ClearMutableValues())
       .WillOnce(WithoutArgs(Invoke([&run_loop]() { run_loop.Quit(); })));
   EXPECT_CALL(*backing_store, CommitPendingWrite()).Times(1);
   pref_store()->ClearMutableValues();
   run_loop.Run();
 }
 
 }  // namespace
 }  // namespace prefs