Remove stale files from lib/html/src.

lib/html/src/TouchEvent.dart

-// Copyright (c) 2011, 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.
-
-interface TouchEvent extends UIEvent default TouchEventWrappingImplementation {
-
-  TouchEvent(TouchList touches, TouchList targetTouches,
-      TouchList changedTouches, String type, Window view, int screenX,
-      int screenY, int clientX, int clientY, [bool ctrlKey, bool altKey,
-      bool shiftKey, bool metaKey]);
-
-  bool get altKey();
-
-  TouchList get changedTouches();
-
-  bool get ctrlKey();
-
-  bool get metaKey();
-
-  bool get shiftKey();
-
-  TouchList get targetTouches();
-
-  TouchList get touches();
-}