Generalize Previews Type code

components/previews/core/previews_io_data.h

Index: components/previews/core/previews_io_data.h
diff --git a/components/previews/core/previews_io_data.h b/components/previews/core/previews_io_data.h
index 5dbf65c9fd494d6ed27f03f1a2bc51ec5b96b7c2..a30ab6ff0764bcf6ce4ce0f443918ca1e6429f42 100644
--- a/components/previews/core/previews_io_data.h
+++ b/components/previews/core/previews_io_data.h
@@ -7,30 +7,31 @@
 
 #include <memory>
 #include <string>
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/single_thread_task_runner.h"
 #include "base/time/time.h"
 #include "components/previews/core/previews_decider.h"
-#include "components/previews/core/previews_opt_out_store.h"
+#include "components/previews/core/previews_experiments.h"
 
 class GURL;
 
 namespace net {
 class URLRequest;
 }
 
 namespace previews {
 class PreviewsBlackList;
+class PreviewsOptOutStore;
 class PreviewsUIService;
 
 // A class to manage the IO portion of inter-thread communication between
 // previews/ objects. Created on the UI thread, but used only on the IO thread
 // after initialization.
 class PreviewsIOData : public PreviewsDecider {
  public:
   PreviewsIOData(
       const scoped_refptr<base::SingleThreadTaskRunner>& ui_task_runner,
       const scoped_refptr<base::SingleThreadTaskRunner>& io_task_runner);