Add some sweet XML classes.

client/html/src/XMLElementWrappingImplementation.dart

Index: client/html/src/XMLElementWrappingImplementation.dart
diff --git a/client/html/src/XMLElementWrappingImplementation.dart b/client/html/src/XMLElementWrappingImplementation.dart
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+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+class _XMLClassSet extends _CssClassSet {
+  _XMLClassSet(element) : super(element);
+
+  String _className() {
+    final classStr = _element.getAttribute('class');
+    return classStr == null ? '' : classStr;
+  }
+
+  void _write(Set s) => _element.setAttribute('class', _formatSet(s));
+}
+
+class XMLElementWrappingImplementation extends ElementWrappingImplementation
+    implements XMLElement {
+  XMLElementWrappingImplementation._wrap(ptr) : super._wrap(ptr);
+
+  factory XMLElementWrappingImplementation.tag(String tag) =>
+    LevelDom.wrapElement(dom.document.createElementNS(null, tag));
+
+  factory XMLElementWrappingImplementation.xml(String xml) {
+    XMLElement parentTag = new XMLElement.tag('xml');
+    parentTag.innerHTML = xml;
+    if (parentTag.nodes.length == 1) return parentTag.nodes.removeLast();
+
+    throw new IllegalArgumentException('XML had ${parentTag.nodes.length} ' +
+        'top-level nodes but 1 expected');
+  }
+
+  Set<String> get classes() {
+    if (_cssClassSet === null) {
+      _cssClassSet = new _XMLClassSet(_ptr);
+    }
+    return _cssClassSet;
+  }
+
+  ElementList get elements() {
+    if (_elements == null) {
+      _elements = new FilteredElementList(this);
+    }
+    return _elements;
+  }
+
+  // TODO: The type of value should be Collection<Element>. See http://b/5392897
+  void set elements(value) {
+    final elements = this.elements;
+    elements.clear();
+    elements.addAll(value);
+  }
+
+  String get outerHTML() {
+    final container = new Element.tag("div");
+    container.elements.add(this.clone(true));
+    return container.innerHTML;
+  }
+
+  String get innerHTML() {
+    final container = new Element.tag("div");
+    container.nodes.addAll(this.clone(true).nodes);
+    return container.innerHTML;
+  }
+
+  void set innerHTML(String xml) {
+    final xmlDoc = new XMLDocument.xml('<xml>$xml</xml>');
+    this.nodes = xmlDoc.nodes;
+  }
+
+  Node _insertAdjacentNode(String where, Node node) {
+    switch (where.toLowerCase()) {
+      case "beforebegin":
+        if (parent == null) return null;
+        parent.insertBefore(node, this);
+        return node;
+      case "afterend":
+        if (parent == null) return null;
+        if (nextNode == null) {
+          parent.nodes.add(node);
+        } else {
+          parent.insertBefore(node, nextNode);
+        }
+        return node;
+      case "afterbegin":
+        this.insertBefore(node, nodes.first);
+        return node;
+      case "beforeend":
+        this.nodes.add(node);
+        return node;
+      default:
+        throw new IllegalArgumentException("Invalid position ${where}");
+    }
+  }
+
+  XMLElement insertAdjacentElement([String where = null,
+      XMLElement element = null]) => this._insertAdjacentNode(where, element);
+
+  void insertAdjacentText([String where = null, String text = null]) {
+    this._insertAdjacentNode(where, new Text(text));
+  }
+
+  void insertAdjacentHTML(
+      [String position_OR_where = null, String text = null]) {
+    this._insertAdjacentNode(
+      position_OR_where, new DocumentFragment.xml(text));
+  }
+
+  Future<ElementRect> get rect() {
+    return _createMeasurementFuture(() => const EmptyElementRect(),
+                                    new Completer<ElementRect>());
+  }
+
+  // For HTML elemens, the default value of "contentEditable" is "inherit", so
+  // we'll use that here as well even though it doesn't really make sense.
+  String get contentEditable() => _attr('contentEditable', 'inherit');
+
+  void set contentEditable(String value) {
+    attributes['contentEditable'] = value;
+  }
+
+  void blur() {}
+  void focus() {}
+  void scrollByLines([int lines = null]) {}
+  void scrollByPages([int pages = null]) {}
+  void scrollIntoView([bool centerIfNeeded = null]) {}
+
+  // Parentless HTML elements return false regardless of the value of their
+  // contentEditable attribute, so XML elements do the same since they're never
+  // actually editable.
+  bool get isContentEditable() => false;
+
+  bool get draggable() => attributes['draggable'] == 'true';
+
+  void set draggable(bool value) { attributes['draggable'] = value.toString(); }
+
+  bool get spellcheck() => attributes['spellcheck'] == 'true';
+
+  void set spellcheck(bool value) {
+    attributes['spellcheck'] = value.toString();
+  }
+
+  bool get hidden() => attributes.containsKey('hidden');
+
+  void set hidden(bool value) {
+    if (value) {
+      attributes['hidden'] = '';
+    } else {
+      attributes.remove('hidden');
+    }
+  }
+
+  int get tabIndex() {
+    try {
+      return Math.parseInt(_attr('tabIndex'));
+    } catch (BadNumberFormatException e) {
+      return 0;
+    }
+  }
+
+  void set tabIndex(int value) { attributes['tabIndex'] = value.toString(); }
+
+  String get id() => _attr('id');
+
+  void set id(String value) { attributes['id'] = value; }
+
+  String get title() => _attr('title');
+
+  void set title(String value) { attributes['title'] = value; }
+
+  String get webkitdropzone() => _attr('webkitdropzone');
+
+  void set webkitdropzone(String value) {
+    attributes['webkitdropzone'] = value;
+  }
+
+  String get lang() => _attr('lang');
+
+  void set lang(String value) { attributes['lang'] = value; }
+
+  String get dir() => _attr('dir');
+
+  void set dir(String value) { attributes['dir'] = value; }
+
+  String _attr(String name, [String def = '']) =>
+    attributes.containsKey(name) ? attributes[name] : def;
+}