Untested hacks to swarm to avoid warnings.

samples-dev/swarm/swarm_ui_lib/touch/Scrollbar.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.
 
 part of touch;
 
 /**
  * Implementation of a scrollbar for the custom scrolling behavior
  * defined in [:Scroller:].
  */
@@ skipping 137 matching lines @@
           // Start hiding immediately if we aren't
           // scrolling or already in the process of
           // hidng the scrollbar
           if (!_scrollInProgress && _timer == null) {
             _boundHideFn();
           }
         });
     }
   }
 
-  void _onStart(UIEvent e) {
+  void _onStart(/*MouseEvent | Touch*/ e) {
     Element elementOver = e.target;
     if (elementOver == _verticalElement ||
         elementOver == _horizontalElement) {
       _currentScrollVertical = elementOver == _verticalElement;
       if (_currentScrollVertical) {
         _currentScrollStartMouse = e.page.y;
         _currentScrollStartOffset = _scroller.getVerticalOffset();
       } else {
         _currentScrollStartMouse = e.page.x;
         _currentScrollStartOffset = _scroller.getHorizontalOffset();
@@ skipping 20 matching lines @@
   void _refreshScrollRatioHelper(num frameSize, num contentSize) {
     num frameTravelDistance = frameSize - _defaultScrollSize(
         frameSize, contentSize) -_PADDING_LENGTH * 2;
     if (frameTravelDistance < 0.001) {
       _currentScrollRatio = 0;
     } else {
       _currentScrollRatio = (contentSize - frameSize) / frameTravelDistance;
     }
   }
 
-  void _onMove(UIEvent e) {
+  void _onMove(/*MouseEvent | Touch*/ e) {
     if (!_scrollBarDragInProgress) {
       return;
     }
     _refreshScrollRatio();
     int coordinate = _currentScrollVertical ? e.page.y : e.page.x;
     num delta = (coordinate - _currentScrollStartMouse) * _currentScrollRatio;
     if (delta != 0) {
       num x;
       num y;
       _currentScrollStartOffset -= delta;
@@ skipping 136 matching lines @@
     style.setProperty(cssPos, '${pos}px', '');
     if (_cachedSize[cssSize] != size) {
       _cachedSize[cssSize] = size;
       style.setProperty(cssSize, '${size}px', '');
     }
     if (element.parent == null) {
       _frame.nodes.add(element);
     }
   }
 }