Reduce the memory usage of bookmarks storage

components/bookmarks/browser/titled_url_node_sorter.h

Index: components/bookmarks/browser/titled_url_node_sorter.h
diff --git a/components/bookmarks/browser/titled_url_node_sorter.h b/components/bookmarks/browser/titled_url_node_sorter.h
index 3327b5980c62167efb66683952d2bd5aca8826ae..7913ef057fae4c370f867345e273c0a94afcb25b 100644
--- a/components/bookmarks/browser/titled_url_node_sorter.h
+++ b/components/bookmarks/browser/titled_url_node_sorter.h
@@ -5,9 +5,10 @@
 #ifndef COMPONENTS_BOOKMARKS_BROWSER_TITLED_URL_NODE_SORTER_H_
 #define COMPONENTS_BOOKMARKS_BROWSER_TITLED_URL_NODE_SORTER_H_
 
-#include <set>
 #include <vector>
 
+#include "base/containers/flat_set.h"
+
 namespace bookmarks {
 
 class TitledUrlNode;
@@ -15,7 +16,7 @@ class TitledUrlNode;
 class TitledUrlNodeSorter {
  public:
   using TitledUrlNodes = std::vector<const TitledUrlNode*>;
-  using TitledUrlNodeSet = std::set<const TitledUrlNode*>;
+  using TitledUrlNodeSet = base::flat_set<const TitledUrlNode*>;
 
   virtual ~TitledUrlNodeSorter() {};