Consistently use ElementTraversal API when looking for an Element

Source/core/rendering/svg/ReferenceFilterBuilder.cpp

Index: Source/core/rendering/svg/ReferenceFilterBuilder.cpp
diff --git a/Source/core/rendering/svg/ReferenceFilterBuilder.cpp b/Source/core/rendering/svg/ReferenceFilterBuilder.cpp
index 4dca2dd72e0bdd427b8343112571fc418b99f3d0..e00f79d8772e6dc10e190bc413184dd9d89e9f7e 100644
--- a/Source/core/rendering/svg/ReferenceFilterBuilder.cpp
+++ b/Source/core/rendering/svg/ReferenceFilterBuilder.cpp
@@ -149,11 +149,11 @@ PassRefPtr<FilterEffect> ReferenceFilterBuilder::build(Filter* parentFilter, Ren
     ColorSpace filterColorSpace = ColorSpaceDeviceRGB;
     bool useFilterColorSpace = getSVGElementColorSpace(filterElement, filterColorSpace);
 
-    for (Node* node = filterElement->firstChild(); node; node = node->nextSibling()) {
-        if (!node->isSVGElement())
+    for (Element* child = ElementTraversal::firstWithin(*filterElement); child; child = ElementTraversal::nextSibling(*child)) {
+        if (!child->isSVGElement())
             continue;
 
-        SVGElement* element = toSVGElement(node);
+        SVGElement* element = toSVGElement(child);
         if (!element->isFilterEffect())
             continue;