anchor.diff:  
     @override
     void domReady() {
  -    // Poach initial Ace <style>s.
  +    // Poach initial Ace <style>s that Ace inserts before the observer in
  +    // [ready] starts listening to new node insertions. See the comment in
  +    // [ready].
       _poachAceStylesAndScripts(document.head.childNodes);
     }
   
  
positive.code: 
    @override
    void ready() {
      // Poach any Ace-related <style>s and <script>s that Ace may dynamically
      // add, e.g. when the editor theme is changed.
      var observer = new MutationObserver((records, _) =>
          records.forEach((r) => _poachAceStylesAndScripts(r.addedNodes))
      )..observe(
  
negative.code:     _fileFilter = $['fileFilter'];
    }
  
    /*
     * Moves any Ace-related <style>s and <script>s in [nodes] from their original
     * parent (which is [document] to this element's [shadowRoot], where the Ace
     * editor's container, which needs them, lives.
     */
    void _poachAceStylesAndScripts(List<Node> nodes) {
      final List<Node> aceNodes = [];
      nodes.forEach((node) {
        if (node is ScriptElement && node.src.contains('ace/src/js') ||
            node is StyleElement && node.id.startsWith('ace') ||
            node is StyleElement && node.innerHtml.contains('ace_')) {
          aceNodes.add(node);
        }
      });
  