Add some sweet XML classes.

client/html/src/XMLDocumentWrappingImplementation.dart

Index: client/html/src/XMLDocumentWrappingImplementation.dart
diff --git a/client/html/src/XMLDocumentWrappingImplementation.dart b/client/html/src/XMLDocumentWrappingImplementation.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 XMLDocumentWrappingImplementation extends DocumentWrappingImplementation
+    implements XMLDocument {
+  // This really just wants to extend both DocumentWrappingImplementation and
+  // XMLElementWrappingImplementation, but since that's not possible we delegate
+  // to the latter.
+  XMLElement documentEl;
+
+  XMLDocumentWrappingImplementation._wrap(documentPtr, ptr) :
+      super._wrap(documentPtr, ptr) {
+    // We want to wrap the pointer in an XMLElement to use its implementation of
+    // various Element methods, but DOMWrapperBase complains if
+    // dartObjectLocalStorage is already set.
+    ptr.dartObjectLocalStorage = null;
+    this.documentEl = new XMLElementWrappingImplementation._wrap(ptr);
+    ptr.dartObjectLocalStorage = this;
+  }
+
+  factory XMLDocumentWrappingImplementation.xml(String xml) {
+    final parser = new dom.DOMParser();
+    final xmlDoc = LevelDom.wrapDocument(
+        parser.parseFromString(xml, 'text/xml'));
+    // When XML parsing fails, the browser creates a document containing a
+    // PARSERERROR element. We want to throw an exception when parsing fails,
+    // but we don't want false positives if the user intends to create a
+    // PARSERERROR element for some reason, so we check for that in the input.
+    //
+    // TODO(nweiz): This is pretty hacky, it would be nice to this some other
+    // way if we can find one.
+    if (!xml.toLowerCase().contains('<parsererror') &&
+        xmlDoc.query('parsererror') != null) {
+      throw new IllegalArgumentException('Error parsing XML: "$xml"');
+    }
+    return xmlDoc;
+  }
+
+  Node get parent() => null;
+
+  Node _insertAdjacentNode(String where, Node node) {
+    switch (where.toLowerCase()) {
+      case "beforebegin":
+        return null;
+      case "afterend":
+        return null;
+      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));
+  }
+
+  XMLElement get activeElement() => null;
+
+  void set body(Element value) {
+    throw new UnsupportedOperationException("XML documents don't have a body.");
+  }
+
+  String get cookie() {
+    throw new UnsupportedOperationException(
+        "XML documents don't support cookies.");
+  }
+
+  void set cookie(String value) {
+    throw new UnsupportedOperationException(
+        "XML documents don't support cookies.");
+  }
+
+  String get manifest() => "";
+
+  void set manifest(String value) {
+    throw new UnsupportedOperationException(
+        "Manifest can't be set for XML documents.");
+  }
+
+  Set<String> get classes() => documentEl.classes;
+
+  ElementList get elements() => documentEl.elements;
+
+  // TODO: The type of value should be Collection<Element>. See http://b/5392897
+  void set elements(value) { documentEl.elements = value; }
+
+  String get outerHTML() => documentEl.outerHTML;
+
+  String get innerHTML() => documentEl.innerHTML;
+
+  void set innerHTML(String xml) { documentEl.innerHTML = xml; }
+
+  String get contentEditable() => documentEl.contentEditable;
+
+  void set contentEditable(String value) { documentEl.contentEditable = value; }
+
+  bool get isContentEditable() => documentEl.isContentEditable;
+
+  bool get draggable() => documentEl.draggable;
+
+  void set draggable(bool value) { documentEl.draggable = value; }
+
+  bool get spellcheck() => documentEl.spellcheck;
+
+  void set spellcheck(bool value) { documentEl.spellcheck = value; }
+
+  bool get hidden() => documentEl.hidden;
+
+  void set hidden(bool value) { documentEl.hidden = value; }
+
+  int get tabIndex() => documentEl.tabIndex;
+
+  void set tabIndex(int value) { documentEl.tabIndex = value; }
+
+  String get id() => documentEl.id;
+
+  void set id(String value) { documentEl.id = value; }
+
+  String get title() => documentEl.title;
+
+  void set title(String value) { documentEl.title = value; }
+
+  String get webkitdropzone() => documentEl.webkitdropzone;
+
+  void set webkitdropzone(String value) { documentEl.webkitdropzone = value; }
+
+  String get lang() => documentEl.lang;
+
+  void set lang(String value) { documentEl.lang = value; }
+
+  String get dir() => documentEl.dir;
+
+  void set dir(String value) { documentEl.dir = value; }
+}