Introduce a layering in the invalidation component as public and impl

components/invalidation/invalidation_prefs.cc

Index: components/invalidation/invalidation_prefs.cc
diff --git a/components/invalidation/invalidation_prefs.cc b/components/invalidation/invalidation_prefs.cc
deleted file mode 100644
index 5f71bd09d7e361bbd98f5ef4478cca80a8257d07..0000000000000000000000000000000000000000
--- a/components/invalidation/invalidation_prefs.cc
+++ /dev/null
@@ -1,22 +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_prefs.h"
-
-namespace invalidation {
-namespace prefs {
-
-// An ID to uniquely identify this client to the invalidator service.
-const char kInvalidatorClientId[] = "invalidator.client_id";
-
-// Opaque state from the invalidation subsystem that is persisted via prefs.
-// The value is base 64 encoded.
-const char kInvalidatorInvalidationState[] = "invalidator.invalidation_state";
-
-// List of received invalidations that have not been acted on by any clients
-// yet.  Used to keep invalidation clients in sync in case of a restart.
-const char kInvalidatorSavedInvalidations[] = "invalidator.saved_invalidations";
-
-}  // namespace prefs
-}  // namespace invalidation