Consider slots as a focus scope

third_party/WebKit/Source/core/dom/shadow/AssignedElementTraversal.h

Index: third_party/WebKit/Source/core/dom/shadow/AssignedElementTraversal.h
diff --git a/third_party/WebKit/Source/core/dom/shadow/AssignedElementTraversal.h b/third_party/WebKit/Source/core/dom/shadow/AssignedElementTraversal.h
new file mode 100644
index 0000000000000000000000000000000000000000..8a52fe6ba65ed195caa38ca63ca0dad2bccc4169
--- /dev/null
+++ b/third_party/WebKit/Source/core/dom/shadow/AssignedElementTraversal.h
@@ -0,0 +1,24 @@
+// 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 AssignedElementTraversal_h
+#define AssignedElementTraversal_h
+
+namespace blink {
+
+class Element;
+class HTMLSlotElement;
+
+class AssignedElementTraversal {
+public:
+    static HTMLSlotElement* slot(const Element& current);

[hayato, 2016/03/03 05:42:22]

Nit: How about renaming this to a more descriptive name? e.g.
assignedSlotOfNearestAncestor

[yuzuchan, 2016/03/04 03:48:37]

Renamed to findScopeOwnerSlot.

+    static Element* assignedAncestor(const Element& current);

[hayato, 2016/03/03 05:42:22]

Nit: How about renaming this function to nearestAncestorAssignedToSlot?

[yuzuchan, 2016/03/04 03:48:37]

Done.

+    static Element* next(const Element& current);
+    static Element* previous(const Element& current);
+    static bool isInAssignedScope(const Element& current);

[hayato, 2016/03/03 05:42:22]

Nit: It might be difficult to understand what isInAssignedScope means. How about
renaming this to isDescendantOfSlot?

[yuzuchan, 2016/03/04 03:48:37]

Renamed to isSlotScoped

+};
+
+} // namespace blink
+
+#endif