[Offline Pages] Duplicate pages when save/delete bookmarks.

components/offline_pages/offline_page_client_policy.h

Index: components/offline_pages/offline_page_client_policy.h
diff --git a/components/offline_pages/offline_page_client_policy.h b/components/offline_pages/offline_page_client_policy.h
index 910b0ddae925f2000b6c34cef748219d3d859e48..de7ae526b0038685b403773c3a2ec1bcd3c14aa0 100644
--- a/components/offline_pages/offline_page_client_policy.h
+++ b/components/offline_pages/offline_page_client_policy.h
@@ -48,6 +48,10 @@ struct OfflinePageClientPolicy {
 
   // Policy to control the lifetime of a page generated by this namespace.
   LifetimePolicy lifetime_policy;
+
+  // How many pages for the same online URL can be stored at any time.
+  // kUnlimitedPages means there's no limit.
+  size_t pages_allowed_per_url;
 };
 
 }  // namespace offline_pages