Support slots' fallback contents in focus navigation

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&);
+    static HTMLSlotElement* findFallbackScopeOwnerSlot(const Element& current);
+    static bool isSlotFallbackScoped(const Element&);
 };
 
 } // namespace blink
 
 #endif