Support slots' fallback contents in focus navigation

third_party/WebKit/Source/core/dom/shadow/SlotScopedTraversal.cpp

Index: third_party/WebKit/Source/core/dom/shadow/SlotScopedTraversal.cpp
diff --git a/third_party/WebKit/Source/core/dom/shadow/SlotScopedTraversal.cpp b/third_party/WebKit/Source/core/dom/shadow/SlotScopedTraversal.cpp
index 92a75f5a96ae3c124304784ec2125fe72cd477c9..82b4123b6fd897f51ad6837db94285fc4748bcd7 100644
--- a/third_party/WebKit/Source/core/dom/shadow/SlotScopedTraversal.cpp
+++ b/third_party/WebKit/Source/core/dom/shadow/SlotScopedTraversal.cpp
@@ -82,4 +82,20 @@ bool SlotScopedTraversal::isSlotScoped(const Element& current)
     return SlotScopedTraversal::nearestAncestorAssignedToSlot(current);
 }
 
+HTMLSlotElement* SlotScopedTraversal::findFallbackScopeOwnerSlot(const Element& current)
+{
+    Element* parent = const_cast<Element*>(current.parentElement());
+    while (parent) {
+        if (isHTMLSlotElement(parent))
+            return toHTMLSlotElement(parent)->getAssignedNodes().isEmpty() ? toHTMLSlotElement(parent) : nullptr;
+        parent = parent->parentElement();
+    }
+    return nullptr;
+}
+
+bool SlotScopedTraversal::isSlotFallbackScoped(const Element& current)
+{
+    return SlotScopedTraversal::findFallbackScopeOwnerSlot(current);
+}
+
 } // namespace blink