Random cleanup of various Dart things in our tree.

sky/sdk/example/mine_digger/lib/main.dart

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 import 'dart:sky' as sky;
 import 'dart:math';
 
 import 'package:sky/rendering/flex.dart';
 import 'package:sky/widgets/basic.dart';
 import 'package:sky/widgets/scaffold.dart';
@@ skipping 288 matching lines @@
     } else {
       // Touch event.
       stopwatch = new Stopwatch()..start();
     }
   }
 
   void _handlePointerUp(sky.PointerEvent event) {
     if (stopwatch == null)
       return;
     // Pointer down was a touch event.
-    var ms = stopwatch.elapsedMilliseconds;
     if (stopwatch.elapsedMilliseconds < 250) {
       game.probe(posX, posY);
     } else {
       // Long press flags.
       game.flag(posX, posY);
     }
     stopwatch = null;
   }
 
   Widget build() {
@@ skipping 44 matching lines @@
   }
 
   Widget build() {
     return game.buildUI();
   }
 }
 
 void main() {
   runApp(new MineDiggerApp());
 }