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 8fdeee786c6043a4c3e045666c81a7e887394d20..e08d54e55da2f5c90cd28f11b6e491676b43b89a 100644
--- a/Source/core/dom/Node.cpp
+++ b/Source/core/dom/Node.cpp
@@ -1140,6 +1140,13 @@ 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();