Adding ClearBlackList to the PreviewsBlackList and plumbing to UI

components/previews/core/previews_opt_out_store.h

Index: components/previews/core/previews_opt_out_store.h
diff --git a/components/previews/core/previews_opt_out_store.h b/components/previews/core/previews_opt_out_store.h
index edcbc0233bd62973fdf33851fca43622cc98b7ab..15aa73f3f9c104ddb354350f64471c207ed37687 100644
--- a/components/previews/core/previews_opt_out_store.h
+++ b/components/previews/core/previews_opt_out_store.h
@@ -44,15 +44,18 @@ class PreviewsOptOutStore {
   // Adds a new navigation to the store. |opt_out| is whether the user opted out
   // of the preview.
   virtual void AddPreviewNavigation(bool opt_out,
                                     const std::string& host_name,
                                     PreviewsType type,
                                     base::Time now) = 0;
 
   // Asynchronously loads a map of host names to PreviewsBlackListItem for that
   // host from the store. And runs |callback| once loading is finished.
   virtual void LoadBlackList(LoadBlackListCallback callback) = 0;
+
+  // Deletes all history in the store between |begin_time| and |end_time|.
+  virtual void ClearBlackList(base::Time begin_time, base::Time end_time) = 0;
 };
 
 }  // namespace previews
 
 #endif  // COMPONENTS_PREVIEWS_CORE_PREVIEWS_OPT_OUT_STORE_H_