Add dummy dart:html library for documentation.

lib/html/doc/interface/TableRowElement.dartdoc

+// 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.
+
+// WARNING:
+//   This file contains documentation that is merged into the real source.
+//   Do not make code changes here.
+
+/// @domName HTMLTableRowElement
+interface TableRowElement extends Element default _Elements {
+
+  TableRowElement();
+
+  /** @domName HTMLTableRowElement.align */
+  String align;
+
+  /** @domName HTMLTableRowElement.bgColor */
+  String bgColor;
+
+  /** @domName HTMLTableRowElement.cells */
+  final HTMLCollection cells;
+
+  /** @domName HTMLTableRowElement.ch */
+  String ch;
+
+  /** @domName HTMLTableRowElement.chOff */
+  String chOff;
+
+  /** @domName HTMLTableRowElement.rowIndex */
+  final int rowIndex;
+
+  /** @domName HTMLTableRowElement.sectionRowIndex */
+  final int sectionRowIndex;
+
+  /** @domName HTMLTableRowElement.vAlign */
+  String vAlign;
+
+  /** @domName HTMLTableRowElement.deleteCell */
+  void deleteCell(int index);
+
+  /** @domName HTMLTableRowElement.insertCell */
+  Element insertCell(int index);
+}