Change NotImplementedException to UnimplementedError.

samples/ui_lib/touch/TouchUtil.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.
 
 /**
  * Wraps a callback with translations of mouse events to touch events. Use
  * this function to invoke your callback that expects touch events after
  * touch events are created from the actual mouse events.
  */
 EventListener mouseToTouchCallback(EventListener callback) {
@@ skipping 148 matching lines @@
   int get pageX => wrapped.pageX;
 
   int get pageY => wrapped.pageY;
 
   int get screenX => wrapped.screenX;
 
   int get screenY {return wrapped.screenY; }
 
   EventTarget get target => wrapped.target;
 
-  num get webkitForce { throw new NotImplementedException(); }
-  int get webkitRadiusX { throw new NotImplementedException(); }
-  int get webkitRadiusY { throw new NotImplementedException(); }
-  num get webkitRotationAngle { throw new NotImplementedException(); }
+  num get webkitForce { throw new UnimplementedError(); }
+  int get webkitRadiusX { throw new UnimplementedError(); }
+  int get webkitRadiusY { throw new UnimplementedError(); }
+  num get webkitRotationAngle { throw new UnimplementedError(); }
 }
 
 class MockTouchEvent implements TouchEvent {
   MouseEvent wrapped;
   // TODO(jacobr): these are currently Lists instead of a TouchList.
   final List<Touch> touches;
   final List<Touch> targetTouches;
   final List<Touch> changedTouches;
   MockTouchEvent(MouseEvent this.wrapped, List<Touch> this.touches,
       List<Touch> this.targetTouches,
@@ skipping 50 matching lines @@
   int get which => wrapped.which;
 
   bool get altKey => wrapped.altKey;
 
   bool get ctrlKey => wrapped.ctrlKey;
 
   bool get metaKey => wrapped.metaKey;
 
   bool get shiftKey => wrapped.shiftKey;
 }