Generalize Previews Type code

components/previews/core/previews_experiments.h

Index: components/previews/core/previews_experiments.h
diff --git a/components/previews/core/previews_experiments.h b/components/previews/core/previews_experiments.h
index 9c8d7add0574d9a8f0a42d6a9bcdd75d41866221..520b45fb65b6cd678159521bb8364288215eab80 100644
--- a/components/previews/core/previews_experiments.h
+++ b/components/previews/core/previews_experiments.h
@@ -20,24 +20,30 @@ size_t MaxInMemoryHostsInBlackList();
 
 // The number of recent navigations that were opted out of that would trigger
 // the host to be blacklisted.
 int BlackListOptOutThreshold();
 
 // The amount of time a host remains blacklisted due to opt outs.
 base::TimeDelta BlackListDuration();
 
 }  // namespace params
 
+enum class PreviewsType {
+  NONE = 0,
+  OFFLINE = 1,
+  LAST = 2,
+};
+
 // Returns true if any client-side previews experiment is active.
 bool IsIncludedInClientSidePreviewsExperimentsFieldTrial();
 
-// Returns true if the field trial that should enable offline pages for
+// Returns true if the field trial that should enable previews for |type| for
 // prohibitvely slow networks is active.
-bool IsOfflinePreviewsEnabled();
+bool IsPreviewsTypeEnabled(PreviewsType type);
 
 // Sets the appropriate state for field trial and variations to imitate the
 // offline pages field trial.
 bool EnableOfflinePreviewsForTesting();
 
 }  // namespace previews
 
 #endif  // COMPONENTS_PREVIEWS_CORE_PREVIEWS_EXPERIMENTS_H_