Have TreeScrope::adoptIfNeeded() take a reference instead of a pointer

Source/core/dom/shadow/ShadowRoot.h

Index: Source/core/dom/shadow/ShadowRoot.h
diff --git a/Source/core/dom/shadow/ShadowRoot.h b/Source/core/dom/shadow/ShadowRoot.h
index 738c7bebc2b8d443ebc7427b388e148621690201..df0b5186c308974e025cf4ffc724ccedeb9959da 100644
--- a/Source/core/dom/shadow/ShadowRoot.h
+++ b/Source/core/dom/shadow/ShadowRoot.h
@@ -166,6 +166,12 @@ inline ShadowRoot* toShadowRoot(Node* node)
     return const_cast<ShadowRoot*>(toShadowRoot(static_cast<const Node*>(node)));
 }
 
+inline ShadowRoot& toShadowRoot(Node& node)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(node.isShadowRoot());
+    return static_cast<ShadowRoot&>(node);
+}
+
 inline const ShadowRoot& toShadowRoot(const Node& node)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(node.isShadowRoot());