Teach V8GCController how to traverse TemplateContentDocumentFragment::host

Source/core/dom/Node.cpp

Index: Source/core/dom/Node.cpp
diff --git a/Source/core/dom/Node.cpp b/Source/core/dom/Node.cpp
index deb789d648f5c49cb255d46064bf1b09c6317e2b..4640e4fc62e28912c07ddf13643dddcfbf69b039 100644
--- a/Source/core/dom/Node.cpp
+++ b/Source/core/dom/Node.cpp
@@ -1146,6 +1146,13 @@ Element* Node::parentOrShadowHostElement() const
     return toElement(parent);
 }
 
+ContainerNode* Node::parentOrShadowHostOrTemplateHostNode() const
+{
+    if (isDocumentFragment() && toDocumentFragment(this)->isTemplateContent())
+        return static_cast<const TemplateContentDocumentFragment*>(this)->host();
+    return parentOrShadowHostNode();
+}
+
 bool Node::isBlockFlowElement() const
 {
     return isElementNode() && renderer() && renderer()->isRenderBlockFlow();