Prepare infrastructure for XML parser.

components/script/dom/servoxmlparser.rs

@@ -2,8 +2,36 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::js::{JS, Root};
 use dom::bindings::reflector::Reflector;
+use dom::bindings::trace::JSTraceable;
+use dom::document::Document;
+use dom::node::Node;
+use dom::text::Text;
+use url::Url;
+use util::str::DOMString;
+use xml5ever::tree_builder::{NodeOrText, TreeSink};
 
+#[must_root]
+#[derive(JSTraceable, HeapSizeOf)]
+pub struct Sink {
+    pub base_url: Option<Url>,
+    pub document: JS<Document>,
+}
+
+impl Sink {
+    #[allow(unrooted_must_root)] // method is only run at parse time
+    pub fn get_or_create(&self, child: NodeOrText<JS<Node>>) -> Root<Node> {
+        match child {
+            NodeOrText::AppendNode(n) => Root::from_ref(&*n),
+            NodeOrText::AppendText(t) => {
+                let s: String = t.into();
+                let text = Text::new(DOMString::from(s), &self.document);
+                Root::upcast(text)
+            }
+        }
+    }
+}
 #[must_root]
 #[dom_struct]
 pub struct ServoXMLParser {