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

Source/core/inspector/InspectorCSSAgent.cpp

Index: Source/core/inspector/InspectorCSSAgent.cpp
diff --git a/Source/core/inspector/InspectorCSSAgent.cpp b/Source/core/inspector/InspectorCSSAgent.cpp
index 6ad444dae3d95d8a5fc4ba1e105afb3773a1ff9b..b870e6b19f28115b79442f316730fe6b92001500 100644
--- a/Source/core/inspector/InspectorCSSAgent.cpp
+++ b/Source/core/inspector/InspectorCSSAgent.cpp
@@ -781,7 +781,7 @@ void InspectorCSSAgent::getPlatformFontsForNode(ErrorString* errorString, int no
             RenderTextFragment* textFragment = toRenderTextFragment(renderer);
             if (textFragment->firstLetter()) {
                 RenderObject* firstLetter = textFragment->firstLetter();
-                for (RenderObject* current = firstLetter->firstChild(); current; current = current->nextSibling()) {
+                for (RenderObject* current = firstLetter->slowFirstChild(); current; current = current->nextSibling()) {
                     if (current->isText())
                         collectPlatformFontsForRenderer(toRenderText(current), &fontStats);
                 }