Introduce a layering in the invalidation component as public and impl

components/invalidation/invalidator_state.cc

Index: components/invalidation/invalidator_state.cc
diff --git a/components/invalidation/invalidator_state.cc b/components/invalidation/invalidator_state.cc
deleted file mode 100644
index 1ad3c45495e17ed15e49efccf6fde0419bfc0c72..0000000000000000000000000000000000000000
--- a/components/invalidation/invalidator_state.cc
+++ /dev/null
@@ -1,25 +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/invalidator_state.h"
-
-#include "base/logging.h"
-
-namespace syncer {
-
-const char* InvalidatorStateToString(InvalidatorState state) {
-  switch (state) {
-    case TRANSIENT_INVALIDATION_ERROR:
-      return "TRANSIENT_INVALIDATION_ERROR";
-    case INVALIDATION_CREDENTIALS_REJECTED:
-      return "INVALIDATION_CREDENTIALS_REJECTED";
-    case INVALIDATIONS_ENABLED:
-      return "INVALIDATIONS_ENABLED";
-    default:
-      NOTREACHED();
-      return "UNKNOWN_INVALIDATOR_STATE";
-  }
-}
-
-}  // namespace syncer