Changed previews component to be a layered component.

components/previews/core/previews_ui_service.h

Index: components/previews/core/previews_ui_service.h
diff --git a/components/previews/previews_ui_service.h b/components/previews/core/previews_ui_service.h
similarity index 88%
rename from components/previews/previews_ui_service.h
rename to components/previews/core/previews_ui_service.h
index 195b0979b82d1d4dd47621ad58888584d25fb0c3..4adc9ad04dc6b135c972dff6f4c0fa6547586af6 100644
--- a/components/previews/previews_ui_service.h
+++ b/components/previews/core/previews_ui_service.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef COMPONENTS_PREVIEWS_PREVIEWS_UI_SERVICE_H_
-#define COMPONENTS_PREVIEWS_PREVIEWS_UI_SERVICE_H_
+#ifndef COMPONENTS_PREVIEWS_CORE_PREVIEWS_UI_SERVICE_H_
+#define COMPONENTS_PREVIEWS_CORE_PREVIEWS_UI_SERVICE_H_
 
 #include <string>
 
@@ -45,4 +45,4 @@ class PreviewsUIService {
 
 }  // namespace previews
 
-#endif  // COMPONENTS_PREVIEWS_PREVIEWS_UI_SERVICE_H_
+#endif  // COMPONENTS_PREVIEWS_CORE_PREVIEWS_UI_SERVICE_H_