Use bookmark creation date fallback for 6 weeks after installing M54

components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h

Index: components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h
diff --git a/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h b/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h
index 1f2aabd146a4e65863de12dedf7a31f9c24dfc00..264465b7dba15d9c07823a91c27424593fafe627 100644
--- a/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h
+++ b/components/ntp_snippets/bookmarks/bookmark_suggestions_provider.h
@@ -14,6 +14,9 @@
 #include "components/ntp_snippets/category_status.h"
 #include "components/ntp_snippets/content_suggestions_provider.h"
 
+class PrefRegistrySimple;
+class PrefService;
+
 namespace gfx {
 class Image;
 }
@@ -26,9 +29,12 @@ class BookmarkSuggestionsProvider : public ContentSuggestionsProvider,
  public:
   BookmarkSuggestionsProvider(ContentSuggestionsProvider::Observer* observer,
                               CategoryFactory* category_factory,
-                              bookmarks::BookmarkModel* bookmark_model);
+                              bookmarks::BookmarkModel* bookmark_model,
+                              PrefService* pref_service);
   ~BookmarkSuggestionsProvider() override;
 
+  static void RegisterProfilePrefs(PrefRegistrySimple* registry);
+
  private:
   // ContentSuggestionsProvider implementation.
   std::vector<Category> GetProvidedCategories() override;
@@ -99,6 +105,11 @@ class BookmarkSuggestionsProvider : public ContentSuggestionsProvider,
   base::Time node_to_change_last_visit_date_;
   base::Time end_of_list_last_visit_date_;
 
+  // TODO(jkrcal): Remove this field and the pref after M55.
+  // For six weeks after first installing M54, this is true and the
+  // fallback implemented in BookmarkLastVisitUtils is activated.
+  bool creation_date_fallback_;
+
   DISALLOW_COPY_AND_ASSIGN(BookmarkSuggestionsProvider);
 };