Generalize Previews Type code

components/previews/core/previews_ui_service.h

Index: components/previews/core/previews_ui_service.h
diff --git a/components/previews/core/previews_ui_service.h b/components/previews/core/previews_ui_service.h
index 74b9512ba00c9fc800a5b8dc35197128057f33c4..12452bcacbec17f23895ac19047030de39f9668a 100644
--- a/components/previews/core/previews_ui_service.h
+++ b/components/previews/core/previews_ui_service.h
@@ -5,20 +5,21 @@
 #ifndef COMPONENTS_PREVIEWS_CORE_PREVIEWS_UI_SERVICE_H_
 #define COMPONENTS_PREVIEWS_CORE_PREVIEWS_UI_SERVICE_H_
 
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/time.h"
+#include "components/previews/core/previews_experiments.h"
 #include "components/previews/core/previews_opt_out_store.h"
 
 class GURL;
 
 namespace base {
 class SingleThreadTaskRunner;
 }
 
 namespace previews {
 class PreviewsIOData;