Have ElementTraversal::firstWithin() take a reference

Source/core/page/FocusController.cpp

Index: Source/core/page/FocusController.cpp
diff --git a/Source/core/page/FocusController.cpp b/Source/core/page/FocusController.cpp
index 6ca0a1a66b1995e3d9249fe66710ae259695830d..cace7b16a7bb85207a7b3ccf867b8b7f11dd2635 100644
--- a/Source/core/page/FocusController.cpp
+++ b/Source/core/page/FocusController.cpp
@@ -767,9 +767,8 @@ static void updateFocusCandidateIfNeeded(FocusDirection direction, const FocusCa
         closest = candidate;
 }
 
-void FocusController::findFocusCandidateInContainer(Node* container, const LayoutRect& startingRect, FocusDirection direction, FocusCandidate& closest)
+void FocusController::findFocusCandidateInContainer(Node& container, const LayoutRect& startingRect, FocusDirection direction, FocusCandidate& closest)
 {
-    ASSERT(container);
     Element* focusedElement = (focusedFrame() && focusedFrame()->document()) ? focusedFrame()->document()->focusedElement() : 0;
 
     Element* element = ElementTraversal::firstWithin(container);
@@ -779,8 +778,8 @@ void FocusController::findFocusCandidateInContainer(Node* container, const Layou
     current.visibleNode = focusedElement;
 
     for (; element; element = (element->isFrameOwnerElement() || canScrollInDirection(element, direction))
-        ? ElementTraversal::nextSkippingChildren(*element, container)
-        : ElementTraversal::next(*element, container)) {
+        ? ElementTraversal::nextSkippingChildren(*element, &container)
+        : ElementTraversal::next(*element, &container)) {
         if (element == focusedElement)
             continue;
 
@@ -791,7 +790,7 @@ void FocusController::findFocusCandidateInContainer(Node* container, const Layou
         if (candidate.isNull())
             continue;
 
-        candidate.enclosingScrollableBox = container;
+        candidate.enclosingScrollableBox = &container;
         updateFocusCandidateIfNeeded(direction, current, candidate, closest);
     }
 }
@@ -808,7 +807,7 @@ bool FocusController::advanceFocusDirectionallyInContainer(Node* container, cons
 
     // Find the closest node within current container in the direction of the navigation.
     FocusCandidate focusCandidate;
-    findFocusCandidateInContainer(container, newStartingRect, direction, focusCandidate);
+    findFocusCandidateInContainer(*container, newStartingRect, direction, focusCandidate);
 
     if (focusCandidate.isNull()) {
         // Nothing to focus, scroll if possible.