Introduce a layering in the invalidation component as public and impl

components/invalidation/base/invalidator_state.h

Index: components/invalidation/base/invalidator_state.h
diff --git a/components/invalidation/invalidator_state.h b/components/invalidation/base/invalidator_state.h
similarity index 74%
rename from components/invalidation/invalidator_state.h
rename to components/invalidation/base/invalidator_state.h
index cee5bd8cdb683ef30fde9be06cbc8a1962e20395..0f0eb385b8ba6e4f393b5bc3e0f00fac7f84a41f 100644
--- a/components/invalidation/invalidator_state.h
+++ b/components/invalidation/base/invalidator_state.h
@@ -2,10 +2,10 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef COMPONENTS_INVALIDATION_INVALIDATOR_STATE_H_
-#define COMPONENTS_INVALIDATION_INVALIDATOR_STATE_H_
+#ifndef COMPONENTS_INVALIDATION_BASE_INVALIDATOR_STATE_H_
+#define COMPONENTS_INVALIDATION_BASE_INVALIDATOR_STATE_H_
 
-#include "components/invalidation/invalidation_export.h"
+#include "components/invalidation/base/invalidation_export.h"
 
 namespace syncer {
 
@@ -28,4 +28,4 @@ INVALIDATION_EXPORT const char* InvalidatorStateToString(
 
 }  // namespace syncer
 
-#endif  // COMPONENTS_INVALIDATION_INVALIDATOR_STATE_H_
+#endif  // COMPONENTS_INVALIDATION_BASE_INVALIDATOR_STATE_H_