Introduce a layering in the invalidation component as public and impl

components/invalidation/public/invalidation.cc

Index: components/invalidation/public/invalidation.cc
diff --git a/components/invalidation/invalidation.cc b/components/invalidation/public/invalidation.cc
similarity index 96%
rename from components/invalidation/invalidation.cc
rename to components/invalidation/public/invalidation.cc
index 8b04e3f52421dc0b42786a082f13c8420d9841d8..26cdb6195ccde983abbf9da3d987f67022a02f19 100644
--- a/components/invalidation/invalidation.cc
+++ b/components/invalidation/public/invalidation.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "components/invalidation/invalidation.h"
+#include "components/invalidation/public/invalidation.h"
 
 #include <cstddef>
 
@@ -12,8 +12,8 @@
 #include "base/rand_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/values.h"
-#include "components/invalidation/ack_handler.h"
-#include "components/invalidation/invalidation_util.h"
+#include "components/invalidation/public/ack_handler.h"
+#include "components/invalidation/public/invalidation_util.h"
 
 namespace syncer {