InlinedVisitor: Migrate xml to use inlined tracing

Source/core/xml/XPathValue.cpp

Index: Source/core/xml/XPathValue.cpp
diff --git a/Source/core/xml/XPathValue.cpp b/Source/core/xml/XPathValue.cpp
index b9bb8877cf900592579c217997deb4bdea61843b..e8fe9e270d22cccfe245a14b894ae5edffaf7217 100644
--- a/Source/core/xml/XPathValue.cpp
+++ b/Source/core/xml/XPathValue.cpp
@@ -38,12 +38,12 @@ namespace XPath {
 
 const Value::AdoptTag Value::adopt = { };
 
-void ValueData::trace(Visitor* visitor)
+DEFINE_TRACE(ValueData)
 {
     visitor->trace(m_nodeSet);
 }
 
-void Value::trace(Visitor* visitor)
+DEFINE_TRACE(Value)
 {
     visitor->trace(m_data);
 }