Remove lib/dom directory!

lib/dom/templates/html/impl/impl_Element.darttemplate

-// 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.
-
-// TODO(jacobr): use _Lists.dart to remove some of the duplicated
-// functionality.
-class _ChildrenElementList implements ElementList {
-  // Raw Element.
-  final _ElementImpl _element;
-  final _HTMLCollectionImpl _childElements;
-
-  _ChildrenElementList._wrap(_ElementImpl element)
-    : _childElements = element.$dom_children,
-      _element = element;
-
-  List<Element> _toList() {
-    final output = new List(_childElements.length);
-    for (int i = 0, len = _childElements.length; i < len; i++) {
-      output[i] = _childElements[i];
-    }
-    return output;
-  }
-
-  _ElementImpl get first() {
-    return _element.$dom_firstElementChild;
-  }
-
-  void forEach(void f(Element element)) {
-    for (_ElementImpl element in _childElements) {
-      f(element);
-    }
-  }
-
-  ElementList filter(bool f(Element element)) {
-    final output = <Element>[];
-    forEach((Element element) {
-      if (f(element)) {
-        output.add(element);
-      }
-    });
-    return new _FrozenElementList._wrap(output);
-  }
-
-  bool every(bool f(Element element)) {
-    for(Element element in this) {
-      if (!f(element)) {
-        return false;
-      }
-    };
-    return true;
-  }
-
-  bool some(bool f(Element element)) {
-    for(Element element in this) {
-      if (f(element)) {
-        return true;
-      }
-    };
-    return false;
-  }
-
-  Collection map(f(Element element)) {
-    final out = [];
-    for (Element el in this) {
-      out.add(f(el));
-    }
-    return out;
-  }
-
-  bool isEmpty() {
-    return _element.$dom_firstElementChild == null;
-  }
-
-  int get length() {
-    return _childElements.length;
-  }
-
-  _ElementImpl operator [](int index) {
-    return _childElements[index];
-  }
-
-  void operator []=(int index, _ElementImpl value) {
-    _element.$dom_replaceChild(value, _childElements[index]);
-  }
-
-   void set length(int newLength) {
-     // TODO(jacobr): remove children when length is reduced.
-     throw const UnsupportedOperationException('');
-   }
-
-  Element add(_ElementImpl value) {
-    _element.$dom_appendChild(value);
-    return value;
-  }
-
-  Element addLast(_ElementImpl value) => add(value);
-
-  Iterator<Element> iterator() => _toList().iterator();
-
-  void addAll(Collection<Element> collection) {
-    for (_ElementImpl element in collection) {
-      _element.$dom_appendChild(element);
-    }
-  }
-
-  void sort(int compare(Element a, Element b)) {
-    throw const UnsupportedOperationException('TODO(jacobr): should we impl?');
-  }
-
-  void setRange(int start, int rangeLength, List from, [int startFrom = 0]) {
-    throw const NotImplementedException();
-  }
-
-  void removeRange(int start, int rangeLength) {
-    throw const NotImplementedException();
-  }
-
-  void insertRange(int start, int rangeLength, [initialValue = null]) {
-    throw const NotImplementedException();
-  }
-
-  List getRange(int start, int rangeLength) =>
-    new _FrozenElementList._wrap(_Lists.getRange(this, start, rangeLength,
-        <Element>[]));
-
-  int indexOf(Element element, [int start = 0]) {
-    return _Lists.indexOf(this, element, start, this.length);
-  }
-
-  int lastIndexOf(Element element, [int start = null]) {
-    if (start === null) start = length - 1;
-    return _Lists.lastIndexOf(this, element, start);
-  }
-
-  void clear() {
-    // It is unclear if we want to keep non element nodes?
-    _element.text = '';
-  }
-
-  Element removeLast() {
-    final result = this.last();
-    if (result != null) {
-      _element.$dom_removeChild(result);
-    }
-    return result;
-  }
-
-  Element last() {
-    return _element.$dom_lastElementChild;
-  }
-}
-
-// TODO(jacobr): this is an inefficient implementation but it is hard to see
-// a better option given that we cannot quite force NodeList to be an
-// ElementList as there are valid cases where a NodeList JavaScript object
-// contains Node objects that are not Elements.
-class _FrozenElementList implements ElementList {
-  final List<Node> _nodeList;
-
-  _FrozenElementList._wrap(this._nodeList);
-
-  Element get first() {
-    return _nodeList[0];
-  }
-
-  void forEach(void f(Element element)) {
-    for (Element el in this) {
-      f(el);
-    }
-  }
-
-  Collection map(f(Element element)) {
-    final out = [];
-    for (Element el in this) {
-      out.add(f(el));
-    }
-    return out;
-  }
-
-  ElementList filter(bool f(Element element)) {
-    final out = new _ElementList([]);
-    for (Element el in this) {
-      if (f(el)) out.add(el);
-    }
-    return out;
-  }
-
-  bool every(bool f(Element element)) {
-    for(Element element in this) {
-      if (!f(element)) {
-        return false;
-      }
-    };
-    return true;
-  }
-
-  bool some(bool f(Element element)) {
-    for(Element element in this) {
-      if (f(element)) {
-        return true;
-      }
-    };
-    return false;
-  }
-
-  bool isEmpty() => _nodeList.isEmpty();
-
-  int get length() => _nodeList.length;
-
-  Element operator [](int index) => _nodeList[index];
-
-  void operator []=(int index, Element value) {
-    throw const UnsupportedOperationException('');
-  }
-
-  void set length(int newLength) {
-    _nodeList.length = newLength;
-  }
-
-  void add(Element value) {
-    throw const UnsupportedOperationException('');
-  }
-
-  void addLast(Element value) {
-    throw const UnsupportedOperationException('');
-  }
-
-  Iterator<Element> iterator() => new _FrozenElementListIterator(this);
-
-  void addAll(Collection<Element> collection) {
-    throw const UnsupportedOperationException('');
-  }
-
-  void sort(int compare(Element a, Element b)) {
-    throw const UnsupportedOperationException('');
-  }
-
-  void setRange(int start, int rangeLength, List from, [int startFrom = 0]) {
-    throw const UnsupportedOperationException('');
-  }
-
-  void removeRange(int start, int rangeLength) {
-    throw const UnsupportedOperationException('');
-  }
-
-  void insertRange(int start, int rangeLength, [initialValue = null]) {
-    throw const UnsupportedOperationException('');
-  }
-
-  ElementList getRange(int start, int rangeLength) =>
-    new _FrozenElementList._wrap(_nodeList.getRange(start, rangeLength));
-
-  int indexOf(Element element, [int start = 0]) =>
-    _nodeList.indexOf(element, start);
-
-  int lastIndexOf(Element element, [int start = null]) =>
-    _nodeList.lastIndexOf(element, start);
-
-  void clear() {
-    throw const UnsupportedOperationException('');
-  }
-
-  Element removeLast() {
-    throw const UnsupportedOperationException('');
-  }
-
-  Element last() => _nodeList.last();
-}
-
-class _FrozenElementListIterator implements Iterator<Element> {
-  final _FrozenElementList _list;
-  int _index = 0;
-
-  _FrozenElementListIterator(this._list);
-
-  /**
-   * Gets the next element in the iteration. Throws a
-   * [NoMoreElementsException] if no element is left.
-   */
-  Element next() {
-    if (!hasNext()) {
-      throw const NoMoreElementsException();
-    }
-
-    return _list[_index++];
-  }
-
-  /**
-   * Returns whether the [Iterator] has elements left.
-   */
-  bool hasNext() => _index < _list.length;
-}
-
-class _ElementList extends _ListWrapper<Element> implements ElementList {
-  _ElementList(List<Element> list) : super(list);
-
-  ElementList filter(bool f(Element element)) =>
-    new _ElementList(super.filter(f));
-
-  ElementList getRange(int start, int rangeLength) =>
-    new _ElementList(super.getRange(start, rangeLength));
-}
-
-class _ElementAttributeMap implements AttributeMap {
-
-  final _ElementImpl _element;
-
-  _ElementAttributeMap(this._element);
-
-  bool containsValue(String value) {
-    final attributes = _element.$dom_attributes;
-    for (int i = 0, len = attributes.length; i < len; i++) {
-      if(value == attributes[i].value) {
-        return true;
-      }
-    }
-    return false;
-  }
-
-  bool containsKey(String key) {
-    return _element.$dom_hasAttribute(key);
-  }
-
-  String operator [](String key) {
-    return _element.$dom_getAttribute(key);
-  }
-
-  void operator []=(String key, value) {
-    _element.$dom_setAttribute(key, '$value');
-  }
-
-  String putIfAbsent(String key, String ifAbsent()) {
-    if (!containsKey(key)) {
-      this[key] = ifAbsent();
-    }
-    return this[key];
-  }
-
-  String remove(String key) {
-    String value = _element.$dom_getAttribute(key);
-    _element.$dom_removeAttribute(key);
-    return value;
-  }
-
-  void clear() {
-    final attributes = _element.$dom_attributes;
-    for (int i = attributes.length - 1; i >= 0; i--) {
-      remove(attributes[i].name);
-    }
-  }
-
-  void forEach(void f(String key, String value)) {
-    final attributes = _element.$dom_attributes;
-    for (int i = 0, len = attributes.length; i < len; i++) {
-      final item = attributes[i];
-      f(item.name, item.value);
-    }
-  }
-
-  Collection<String> getKeys() {
-    // TODO(jacobr): generate a lazy collection instead.
-    final attributes = _element.$dom_attributes;
-    final keys = new List<String>(attributes.length);
-    for (int i = 0, len = attributes.length; i < len; i++) {
-      keys[i] = attributes[i].name;
-    }
-    return keys;
-  }
-
-  Collection<String> getValues() {
-    // TODO(jacobr): generate a lazy collection instead.
-    final attributes = _element.$dom_attributes;
-    final values = new List<String>(attributes.length);
-    for (int i = 0, len = attributes.length; i < len; i++) {
-      values[i] = attributes[i].value;
-    }
-    return values;
-  }
-
-  /**
-   * The number of {key, value} pairs in the map.
-   */
-  int get length() {
-    return _element.$dom_attributes.length;
-  }
-
-  /**
-   * Returns true if there is no {key, value} pair in the map.
-   */
-  bool isEmpty() {
-    return length == 0;
-  }
-}
-
-/**
- * Provides a Map abstraction on top of data-* attributes, similar to the
- * dataSet in the old DOM.
- */
-class _DataAttributeMap implements AttributeMap {
-
-  final Map<String, String> $dom_attributes;
-
-  _DataAttributeMap(this.$dom_attributes);
-
-  // interface Map
-
-  // TODO: Use lazy iterator when it is available on Map.
-  bool containsValue(String value) => getValues().some((v) => v == value);
-
-  bool containsKey(String key) => $dom_attributes.containsKey(_attr(key));
-
-  String operator [](String key) => $dom_attributes[_attr(key)];
-
-  void operator []=(String key, value) {
-    $dom_attributes[_attr(key)] = '$value';
-  }
-
-  String putIfAbsent(String key, String ifAbsent()) =>
-    $dom_attributes.putIfAbsent(_attr(key), ifAbsent);
-
-  String remove(String key) => $dom_attributes.remove(_attr(key));
-
-  void clear() {
-    // Needs to operate on a snapshot since we are mutating the collection.
-    for (String key in getKeys()) {
-      remove(key);
-    }
-  }
-
-  void forEach(void f(String key, String value)) {
-    $dom_attributes.forEach((String key, String value) {
-      if (_matches(key)) {
-        f(_strip(key), value);
-      }
-    });
-  }
-
-  Collection<String> getKeys() {
-    final keys = new List<String>();
-    $dom_attributes.forEach((String key, String value) {
-      if (_matches(key)) {
-        keys.add(_strip(key));
-      }
-    });
-    return keys;
-  }
-
-  Collection<String> getValues() {
-    final values = new List<String>();
-    $dom_attributes.forEach((String key, String value) {
-      if (_matches(key)) {
-        values.add(value);
-      }
-    });
-    return values;
-  }
-
-  int get length() => getKeys().length;
-
-  // TODO: Use lazy iterator when it is available on Map.
-  bool isEmpty() => length == 0;
-
-  // Helpers.
-  String _attr(String key) => 'data-$key';
-  bool _matches(String key) => key.startsWith('data-');
-  String _strip(String key) => key.substring(5);
-}
-
-class _CssClassSet implements CSSClassSet {
-
-  final _ElementImpl _element;
-
-  _CssClassSet(this._element);
-
-  String toString() => _formatSet(_read());
-
-  // interface Iterable - BEGIN
-  Iterator<String> iterator() => _read().iterator();
-  // interface Iterable - END
-
-  // interface Collection - BEGIN
-  void forEach(void f(String element)) {
-    _read().forEach(f);
-  }
-
-  Collection map(f(String element)) => _read().map(f);
-
-  Collection<String> filter(bool f(String element)) => _read().filter(f);
-
-  bool every(bool f(String element)) => _read().every(f);
-
-  bool some(bool f(String element)) => _read().some(f);
-
-  bool isEmpty() => _read().isEmpty();
-
-  bool get isFrozen() => false;
-
-  int get length() =>_read().length;
-
-  // interface Collection - END
-
-  // interface Set - BEGIN
-  bool contains(String value) => _read().contains(value);
-
-  void add(String value) {
-    // TODO - figure out if we need to do any validation here
-    // or if the browser natively does enough
-    _modify((s) => s.add(value));
-  }
-
-  bool remove(String value) {
-    Set<String> s = _read();
-    bool result = s.remove(value);
-    _write(s);
-    return result;
-  }
-
-  bool toggle(String value) {
-    Set<String> s = _read();
-    bool result = false;
-    if (s.contains(value)) {
-      s.remove(value);
-    } else {
-      s.add(value);
-      result = true;
-    }
-    _write(s);
-    return result;
-  }
-
-  void addAll(Collection<String> collection) {
-    // TODO - see comment above about validation
-    _modify((s) => s.addAll(collection));
-  }
-
-  void removeAll(Collection<String> collection) {
-    _modify((s) => s.removeAll(collection));
-  }
-
-  bool isSubsetOf(Collection<String> collection) =>
-    _read().isSubsetOf(collection);
-
-  bool containsAll(Collection<String> collection) =>
-    _read().containsAll(collection);
-
-  Set<String> intersection(Collection<String> other) =>
-    _read().intersection(other);
-
-  void clear() {
-    _modify((s) => s.clear());
-  }
-  // interface Set - END
-
-  /**
-   * Helper method used to modify the set of css classes on this element.
-   *
-   *   f - callback with:
-   *      s - a Set of all the css class name currently on this element.
-   *
-   *   After f returns, the modified set is written to the
-   *       className property of this element.
-   */
-  void _modify( f(Set<String> s)) {
-    Set<String> s = _read();
-    f(s);
-    _write(s);
-  }
-
-  /**
-   * Read the class names from the Element class property,
-   * and put them into a set (duplicates are discarded).
-   */
-  Set<String> _read() {
-    // TODO(mattsh) simplify this once split can take regex.
-    Set<String> s = new Set<String>();
-    for (String name in _classname().split(' ')) {
-      String trimmed = name.trim();
-      if (!trimmed.isEmpty()) {
-        s.add(trimmed);
-      }
-    }
-    return s;
-  }
-
-  /**
-   * Read the class names as a space-separated string. This is meant to be
-   * overridden by subclasses.
-   */
-  String _classname() => _element.$dom_className;
-
-  /**
-   * Join all the elements of a set into one string and write
-   * back to the element.
-   */
-  void _write(Set s) {
-    _element.$dom_className = _formatSet(s);
-  }
-
-  String _formatSet(Set<String> s) {
-    // TODO(mattsh) should be able to pass Set to String.joins http:/b/5398605
-    List list = new List.from(s);
-    return Strings.join(list, ' ');
-  }
-}
-
-class _SimpleClientRect implements ClientRect {
-  final num left;
-  final num top;
-  final num width;
-  final num height;
-  num get right() => left + width;
-  num get bottom() => top + height;
-
-  const _SimpleClientRect(this.left, this.top, this.width, this.height);
-
-  bool operator ==(ClientRect other) {
-    return other !== null && left == other.left && top == other.top
-        && width == other.width && height == other.height;
-  }
-
-  String toString() => "($left, $top, $width, $height)";
-}
-
-// TODO(jacobr): we cannot currently be lazy about calculating the client
-// rects as we must perform all measurement queries at a safe point to avoid
-// triggering unneeded layouts.
-/**
- * All your element measurement needs in one place
- * @domName none
- */
-class _ElementRectImpl implements ElementRect {
-  final ClientRect client;
-  final ClientRect offset;
-  final ClientRect scroll;
-
-  // TODO(jacobr): should we move these outside of ElementRect to avoid the
-  // overhead of computing them every time even though they are rarely used.
-  final _ClientRectImpl _boundingClientRect;
-  final _ClientRectListImpl _clientRects;
-
-  _ElementRectImpl(_ElementImpl element) :
-    client = new _SimpleClientRect(element.$dom_clientLeft,
-                                  element.$dom_clientTop,
-                                  element.$dom_clientWidth,
-                                  element.$dom_clientHeight),
-    offset = new _SimpleClientRect(element.$dom_offsetLeft,
-                                  element.$dom_offsetTop,
-                                  element.$dom_offsetWidth,
-                                  element.$dom_offsetHeight),
-    scroll = new _SimpleClientRect(element.$dom_scrollLeft,
-                                  element.$dom_scrollTop,
-                                  element.$dom_scrollWidth,
-                                  element.$dom_scrollHeight),
-    _boundingClientRect = element.$dom_getBoundingClientRect(),
-    _clientRects = element.$dom_getClientRects();
-
-  _ClientRectImpl get bounding() => _boundingClientRect;
-
-  // TODO(jacobr): cleanup.
-  List<ClientRect> get clientRects() {
-    final out = new List(_clientRects.length);
-    for (num i = 0; i < _clientRects.length; i++) {
-      out[i] = _clientRects.item(i);
-    }
-    return out;
-  }
-}
-
-class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
-
-  /**
-   * @domName Element.hasAttribute, Element.getAttribute, Element.setAttribute,
-   *   Element.removeAttribute
-   */
-  _ElementAttributeMap get attributes() => new _ElementAttributeMap(this);
-
-  void set attributes(Map<String, String> value) {
-    Map<String, String> attributes = this.attributes;
-    attributes.clear();
-    for (String key in value.getKeys()) {
-      attributes[key] = value[key];
-    }
-  }
-
-  void set elements(Collection<Element> value) {
-    final elements = this.elements;
-    elements.clear();
-    elements.addAll(value);
-  }
-
-  ElementList get elements() => new _ChildrenElementList._wrap(this);
-
-  _ElementImpl query(String selectors) => $dom_querySelector(selectors);
-
-  List<Element> queryAll(String selectors) =>
-    new _FrozenElementList._wrap($dom_querySelectorAll(selectors));
-
-  _CssClassSet get classes() => new _CssClassSet(this);
-
-  void set classes(Collection<String> value) {
-    _CssClassSet classSet = classes;
-    classSet.clear();
-    classSet.addAll(value);
-  }
-
-  Map<String, String> get dataAttributes() =>
-    new _DataAttributeMap(attributes);
-
-  void set dataAttributes(Map<String, String> value) {
-    final dataAttributes = this.dataAttributes;
-    dataAttributes.clear();
-    for (String key in value.getKeys()) {
-      dataAttributes[key] = value[key];
-    }
-  }
-
-  Future<ElementRect> get rect() {
-    return _createMeasurementFuture(
-        () => new _ElementRectImpl(this),
-        new Completer<ElementRect>());
-  }
-
-  Future<CSSStyleDeclaration> get computedStyle() {
-     // TODO(jacobr): last param should be null, see b/5045788
-     return getComputedStyle('');
-  }
-
-  Future<CSSStyleDeclaration> getComputedStyle(String pseudoElement) {
-    return _createMeasurementFuture(
-        () => _window.$dom_getComputedStyle(this, pseudoElement),
-        new Completer<CSSStyleDeclaration>());
-  }
-
-  void addText(String text) {
-    this.insertAdjacentText('beforeend', text);
-  }
-
-  void addHTML(String text) {
-    this.insertAdjacentHTML('beforeend', text);
-  }
-
-  // Hooks to support custom WebComponents.
-  var xtag;
-
-$if DARTIUM
-  noSuchMethod(String name, List args) {
-    if (dynamicUnknownElementDispatcher == null) {
-      throw new NoSuchMethodException(this, name, args);
-    } else {
-      return dynamicUnknownElementDispatcher(this, name, args);
-    }
-  }
-$else
-  // TODO(vsm): Implement noSuchMethod or similar for dart2js.
-$endif
-
-$if DART2JS
-  /** @domName Element.insertAdjacentText */
-  void insertAdjacentText(String where, String text) {
-    if (JS('bool', '!!this.insertAdjacentText')) {
-      _insertAdjacentText(where, text);
-    } else {
-      _insertAdjacentNode(where, new Text(text));
-    }
-  }
-
-  void _insertAdjacentText(String where, String text)
-      native 'insertAdjacentText';
-
-  /** @domName Element.insertAdjacentHTML */
-  void insertAdjacentHTML(String where, String text) {
-    if (JS('bool', '!!this.insertAdjacentHTML')) {
-      _insertAdjacentHTML(where, text);
-    } else {
-      _insertAdjacentNode(where, new DocumentFragment.html(text));
-    }
-  }
-
-  void _insertAdjacentHTML(String where, String text)
-      native 'insertAdjacentHTML';
-
-  /** @domName Element.insertAdjacentHTML */
-  Element insertAdjacentElement(String where, Element element) {
-    if (JS('bool', '!!this.insertAdjacentElement')) {
-      _insertAdjacentElement(where, element);
-    } else {
-      _insertAdjacentNode(where, element);
-    }
-    return element;
-  }
-
-  void _insertAdjacentElement(String where, Element element)
-      native 'insertAdjacentElement';
-
-  void _insertAdjacentNode(String where, Node node) {
-    switch (where.toLowerCase()) {
-      case 'beforebegin':
-        this.parent.insertBefore(node, this);
-        break;
-      case 'afterbegin':
-        this.insertBefore(node, this.nodes.first);
-        break;
-      case 'beforeend':
-        this.nodes.add(node);
-        break;
-      case 'afterend':
-        this.parent.insertBefore(node, this.nextNode);
-        break;
-      default:
-        throw new IllegalArgumentException("Invalid position ${where}");
-    }
-  }
-$else
-$endif
-
-$!MEMBERS
-}
-
-// Temporary dispatch hook to support WebComponents.
-Function dynamicUnknownElementDispatcher;
-
-final _START_TAG_REGEXP = const RegExp('<(\\w+)');
-class _ElementFactoryProvider {
-  static final _CUSTOM_PARENT_TAG_MAP = const {
-    'body' : 'html',
-    'head' : 'html',
-    'caption' : 'table',
-    'td': 'tr',
-    'colgroup': 'table',
-    'col' : 'colgroup',
-    'tr' : 'tbody',
-    'tbody' : 'table',
-    'tfoot' : 'table',
-    'thead' : 'table',
-    'track' : 'audio',
-  };
-
-  /** @domName Document.createElement */
-  factory Element.html(String html) {
-    // TODO(jacobr): this method can be made more robust and performant.
-    // 1) Cache the dummy parent elements required to use innerHTML rather than
-    //    creating them every call.
-    // 2) Verify that the html does not contain leading or trailing text nodes.
-    // 3) Verify that the html does not contain both <head> and <body> tags.
-    // 4) Detatch the created element from its dummy parent.
-    String parentTag = 'div';
-    String tag;
-    final match = _START_TAG_REGEXP.firstMatch(html);
-    if (match !== null) {
-      tag = match.group(1).toLowerCase();
-      if (_CUSTOM_PARENT_TAG_MAP.containsKey(tag)) {
-        parentTag = _CUSTOM_PARENT_TAG_MAP[tag];
-      }
-    }
-    final _ElementImpl temp = new Element.tag(parentTag);
-    temp.innerHTML = html;
-
-    Element element;
-    if (temp.elements.length == 1) {
-      element = temp.elements.first;
-    } else if (parentTag == 'html' && temp.elements.length == 2) {
-      // Work around for edge case in WebKit and possibly other browsers where
-      // both body and head elements are created even though the inner html
-      // only contains a head or body element.
-      element = temp.elements[tag == 'head' ? 0 : 1];
-    } else {
-      throw new IllegalArgumentException('HTML had ${temp.elements.length} '
-          'top level elements but 1 expected');
-    }
-    element.remove();
-    return element;
-  }
-
-  /** @domName Document.createElement */
-$if DART2JS
-  // Optimization to improve performance until the dart2js compiler inlines this
-  // method.
-  factory Element.tag(String tag) native "return document.createElement(tag)";
-$else
-  factory Element.tag(String tag) => _document.$dom_createElement(tag);
-$endif
-}