Consider slots as a focus scope

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

Index: third_party/WebKit/Source/core/dom/AssignedElementTraversal.h
diff --git a/third_party/WebKit/Source/core/dom/AssignedElementTraversal.h b/third_party/WebKit/Source/core/dom/AssignedElementTraversal.h
new file mode 100644
index 0000000000000000000000000000000000000000..deaeb63da259ba11ae1a22b4f448f17459f9d5fd
--- /dev/null
+++ b/third_party/WebKit/Source/core/dom/AssignedElementTraversal.h
@@ -0,0 +1,22 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.

[kochi, 2016/03/01 12:55:40]

2016?

[yuzuchan, 2016/03/02 09:02:14]

Done.

+// 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
+
+#include "core/dom/Element.h"
+#include "core/html/HTMLSlotElement.h"
+
+namespace blink {

[kochi, 2016/03/01 12:55:40]

It would be enough to insert forward declarations of

class Element;
class HTMLSlotElement;

here (in namespace blink) and you can remove the 2 includes above.
(then of course, you need to include them in .cpp file, but you already do :) )

note: forward declaration is preferred to #include to make the compile time
shorter for
those .cpp which includes this header.

[yuzuchan, 2016/03/02 09:02:14]

Done.

+class AssignedElementTraversal {
+public:
+    static HTMLSlotElement* slot(const Element& current);
+    static Element* assignedAncestor(const Element& current);
+    static Element* next(const Element& current);
+    static Element* previous(const Element& current);
+    static bool isInAssignedScope(const Element& current);
+};
+} // namespace blink
+
+#endif