Introduce a layering in the invalidation component as public and impl

components/invalidation/invalidation_state_tracker.cc

Index: components/invalidation/invalidation_state_tracker.cc
diff --git a/components/invalidation/invalidation_state_tracker.cc b/components/invalidation/invalidation_state_tracker.cc
deleted file mode 100644
index 4bc79df4e5415e15a158bff6171e2bb28b05c29b..0000000000000000000000000000000000000000
--- a/components/invalidation/invalidation_state_tracker.cc
+++ /dev/null
@@ -1,13 +0,0 @@
-// Copyright 2014 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 "components/invalidation/invalidation_state_tracker.h"
-
-namespace syncer {
-
-InvalidationStateTracker::InvalidationStateTracker() {}
-
-InvalidationStateTracker::~InvalidationStateTracker() {}
-
-}  // namespace syncer