Factor out bookmark-specific sorting logic from BookmarkIndex

components/bookmarks/browser/titled_url_node_sorter.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef COMPONENTS_BOOKMARKS_BROWSER_TITLED_URL_NODE_SORTER_H_
+#define COMPONENTS_BOOKMARKS_BROWSER_TITLED_URL_NODE_SORTER_H_
+
+#include <set>
+#include <vector>
+
+namespace bookmarks {
+
+class TitledUrlNode;
+
+class TitledUrlNodeSorter {
+ public:
+  using TitledUrlNodes = std::vector<const TitledUrlNode*>;
+  using TitledUrlNodeSet = std::set<const TitledUrlNode*>;
+
+  virtual ~TitledUrlNodeSorter() {};
+
+  // Sorts |matches| in an implementation-specific way, placing the results in
+  // |sorted_nodes|.
+  virtual void SortMatches(const TitledUrlNodeSet& matches,
+                           TitledUrlNodes* sorted_nodes) const = 0;
+};
+
+}  // namespace bookmarks
+
+#endif  // COMPONENTS_BOOKMARKS_BROWSER_TITLED_URL_NODE_SORTER_H_