Have ElementTraversal / NodeTraversal's next() methods take a reference

Source/core/html/track/TextTrackCue.cpp

Index: Source/core/html/track/TextTrackCue.cpp
diff --git a/Source/core/html/track/TextTrackCue.cpp b/Source/core/html/track/TextTrackCue.cpp
index e793d8642c8d383ccae74b3b92543fdc0289614d..4b19353f062095f5838ed2f4f135ea4a941beae8 100644
--- a/Source/core/html/track/TextTrackCue.cpp
+++ b/Source/core/html/track/TextTrackCue.cpp
@@ -628,7 +628,7 @@ void TextTrackCue::determineTextDirection()
     // pre-order, depth-first traversal, excluding WebVTT Ruby Text Objects and
     // their descendants.
     StringBuilder paragraphBuilder;
-    for (Node* node = m_webVTTNodeTree->firstChild(); node; node = NodeTraversal::next(node, m_webVTTNodeTree.get())) {
+    for (Node* node = m_webVTTNodeTree->firstChild(); node; node = NodeTraversal::next(*node, m_webVTTNodeTree.get())) {
         if (!node->isTextNode() || node->localName() == rtTag)
             continue;
 
@@ -787,7 +787,7 @@ void TextTrackCue::markFutureAndPastNodes(ContainerNode* root, double previousTi
     if (currentTimestamp > movieTime)
         isPastNode = false;
 
-    for (Node* child = root->firstChild(); child; child = NodeTraversal::next(child, root)) {
+    for (Node* child = root->firstChild(); child; child = NodeTraversal::next(*child, root)) {
         if (child->nodeName() == timestampTag) {
             unsigned position = 0;
             String timestamp = child->nodeValue();