Remove the old hand-written HTML doc format, which has not worked for months.

tools/dom/doc/interface/UIEvent.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: Do not edit - generated code.
-
-/// @domName UIEvent
-abstract class UIEvent implements Event {
-
-  /** @domName UIEvent.charCode */
-  abstract int get charCode;
-
-  /** @domName UIEvent.detail */
-  abstract int get detail;
-
-  /** @domName UIEvent.keyCode */
-  abstract int get keyCode;
-
-  /** @domName UIEvent.layerX */
-  abstract int get layerX;
-
-  /** @domName UIEvent.layerY */
-  abstract int get layerY;
-
-  /** @domName UIEvent.pageX */
-  abstract int get pageX;
-
-  /** @domName UIEvent.pageY */
-  abstract int get pageY;
-
-  /** @domName UIEvent.view */
-  abstract Window get view;
-
-  /** @domName UIEvent.which */
-  abstract int get which;
-
-  /** @domName UIEvent.initUIEvent */
-  void initUIEvent(String type, bool canBubble, bool cancelable, LocalWindow view, int detail);
-}