[oilpan] Implement accept methods to trace the class hierarchy of SVGElement and all sub-classes.

Source/core/svg/SVGElement.cpp

Index: Source/core/svg/SVGElement.cpp
diff --git a/Source/core/svg/SVGElement.cpp b/Source/core/svg/SVGElement.cpp
index 2819e53a9e25212f782734ee4648eeee2c9e19c8..e7ff678971638bac950f2b17d5576a4d4fcd3b7c 100644
--- a/Source/core/svg/SVGElement.cpp
+++ b/Source/core/svg/SVGElement.cpp
@@ -445,6 +445,11 @@ bool SVGElement::removeEventListener(const AtomicString& eventType, EventListene
     return true;
 }
 
+void SVGElement::accept(Visitor* visitor) const
+{
+    StyledElement::accept(visitor);
+}
+
 static bool hasLoadListener(Element* element)
 {
     if (element->hasEventListeners(eventNames().loadEvent))