add 'slow' prefix to RenderObject's firstChild() / lastChild() methods

Source/core/rendering/RenderTreeAsText.cpp

Index: Source/core/rendering/RenderTreeAsText.cpp
diff --git a/Source/core/rendering/RenderTreeAsText.cpp b/Source/core/rendering/RenderTreeAsText.cpp
index ed59e0fd92ad051856638f5307f4e128372a72f6..393f6c687ea624cbb9cc61e8b7ca33f72985eff6 100644
--- a/Source/core/rendering/RenderTreeAsText.cpp
+++ b/Source/core/rendering/RenderTreeAsText.cpp
@@ -474,7 +474,7 @@ void write(TextStream& ts, const RenderObject& o, int indent, RenderAsTextBehavi
         }
     }
 
-    for (RenderObject* child = o.firstChild(); child; child = child->nextSibling()) {
+    for (RenderObject* child = o.slowFirstChild(); child; child = child->nextSibling()) {
         if (child->hasLayer())
             continue;
         write(ts, *child, indent + 1, behavior);
@@ -736,7 +736,7 @@ String externalRepresentation(Element* element, RenderAsTextBehavior behavior)
 
 static void writeCounterValuesFromChildren(TextStream& stream, RenderObject* parent, bool& isFirstCounter)
 {
-    for (RenderObject* child = parent->firstChild(); child; child = child->nextSibling()) {
+    for (RenderObject* child = parent->slowFirstChild(); child; child = child->nextSibling()) {
         if (child->isCounter()) {
             if (!isFirstCounter)
                 stream << " ";