Fix focus navigation for nested slot case

third_party/WebKit/Source/core/page/FocusController.cpp

Index: third_party/WebKit/Source/core/page/FocusController.cpp
diff --git a/third_party/WebKit/Source/core/page/FocusController.cpp b/third_party/WebKit/Source/core/page/FocusController.cpp
index 180f66033404f3c61646f90656a2bfed7c524918..923712914c47a0a149f0df898ff8ed6b9b38b66a 100644
--- a/third_party/WebKit/Source/core/page/FocusController.cpp
+++ b/third_party/WebKit/Source/core/page/FocusController.cpp
@@ -171,13 +171,7 @@ void ScopedFocusNavigation::moveToPrevious() {
 void ScopedFocusNavigation::moveToFirst() {
   if (m_rootSlot) {
     if (!m_slotFallbackTraversal) {
-      HeapVector<Member<Node>> assignedNodes = m_rootSlot->assignedNodes();
-      for (auto assignedNode : assignedNodes) {
-        if (assignedNode->isElementNode()) {
-          m_current = toElement(assignedNode);
-          break;
-        }
-      }
+      m_current = SlotScopedTraversal::firstAssignedToSlot(*m_rootSlot);
     } else {
       Element* first = ElementTraversal::firstChild(*m_rootSlot);
       while (first &&
@@ -200,15 +194,7 @@ void ScopedFocusNavigation::moveToFirst() {
 void ScopedFocusNavigation::moveToLast() {
   if (m_rootSlot) {
     if (!m_slotFallbackTraversal) {
-      HeapVector<Member<Node>> assignedNodes = m_rootSlot->assignedNodes();
-      for (auto assignedNode = assignedNodes.rbegin();
-           assignedNode != assignedNodes.rend(); ++assignedNode) {
-        if ((*assignedNode)->isElementNode()) {
-          m_current =
-              ElementTraversal::lastWithinOrSelf(*toElement(*assignedNode));
-          break;
-        }
-      }
+      m_current = SlotScopedTraversal::lastAssignedToSlot(*m_rootSlot);
     } else {
       Element* last = ElementTraversal::lastWithin(*m_rootSlot);
       while (last &&