Consider slots as a focus scope

third_party/WebKit/Source/core/dom/shadow/SlotScopedTraversal.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 SlotScopedTraversal_h
+#define SlotScopedTraversal_h
+
+namespace blink {
+
+class Element;
+class HTMLSlotElement;
+
+class SlotScopedTraversal {
+public:
+    static HTMLSlotElement* findScopeOwnerSlot(const Element&);
+    static Element* nearestAncestorAssignedToSlot(const Element&);
+    static Element* next(const Element&);
+    static Element* previous(const Element&);
+    static bool isSlotScoped(const Element&);
+};
+
+} // namespace blink
+
+#endif