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

Source/core/rendering/RenderObject.h

Index: Source/core/rendering/RenderObject.h
diff --git a/Source/core/rendering/RenderObject.h b/Source/core/rendering/RenderObject.h
index 3f6f76e6eca7bb84f71780ea28b945228ef905f7..83a96106c1aea6c0db23c03709a674db9cf26431 100644
--- a/Source/core/rendering/RenderObject.h
+++ b/Source/core/rendering/RenderObject.h
@@ -170,18 +170,13 @@ public:
     RenderObject* previousSibling() const { return m_previous; }
     RenderObject* nextSibling() const { return m_next; }
 
-    // FIXME: These should be renamed slowFirstChild, slowLastChild, etc.
-    // to discourage their use. The virtualChildren() call inside these
-    // can be slow for hot code paths.
-    // Currently, some subclasses like RenderBlock, override these NON-virtual
-    // functions to make these fast when we already have a more specific pointer type.
-    RenderObject* firstChild() const
+    RenderObject* slowFirstChild() const
     {
         if (const RenderObjectChildList* children = virtualChildren())
             return children->firstChild();
         return 0;
     }
-    RenderObject* lastChild() const
+    RenderObject* slowLastChild() const
     {
         if (const RenderObjectChildList* children = virtualChildren())
             return children->lastChild();