Partial fix to client breakage

client/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.
 
 /**
  * Implementation of a scrollbar for the custom scrolling behavior
  * defined in [:Scroller:].
  */
 class Scrollbar implements ScrollListener {
   /**
@@ skipping 37 matching lines @@
 
   int _currentScrollStartMouse;
   num _currentScrollStartOffset;
   bool _currentScrollVertical;
   num _currentScrollRatio;
   num _timerId;
 
   bool _displayOnHover;
   bool _hovering = false;
 
-  Scrollbar(Scroller scroller, [this._displayOnHover = true]) :
+  Scrollbar(Scroller scroller, [displayOnHover = true]) :
+      _displayOnHover = displayOnHover,
       _scroller = scroller,
       _frame = scroller.getFrame(),
       _cachedSize = new Map<String, num>() {
     _boundHideFn = () { _showScrollbars(false); };
   }
 
   bool get _scrollBarDragInProgress() => _scrollBarDragInProgressValue;
 
   void set _scrollBarDragInProgress(bool value) {
     _scrollBarDragInProgressValue = value;
@@ skipping 273 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);
     }
   }
 }