Tighten up a bunch of types in test.dart.

tools/testing/dart/co19_test.dart

 // Copyright (c) 2012, 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.
 
 /**
  * Tool for running co19 tests. Used when updating co19.
  *
  * Currently, this tool is merely a convenience around multiple
  * invocations of test.dart. Long term, we hope to evolve this into a
  * script that can automate most of the tasks necessary when updating
@@ skipping 42 matching lines @@
     '-cnone',
     '--use-sdk',
     '--fast-startup'
   ],
   const <String>['-mrelease', '-rdartium', '-cnone', '--use-sdk'],
 ];
 
 void main(List<String> args) {
   TestUtils.setDartDirUri(Platform.script.resolve('../../..'));
   var optionsParser = new TestOptionsParser();
-  List<Map> configurations = <Map>[];
+  var configurations = <Map>[];
   for (var commandLine in COMMAND_LINES) {
-    List arguments = <String>[];
+    var arguments = <String>[];
     arguments.addAll(COMMON_ARGUMENTS);
     arguments.addAll(args);
     arguments.addAll(commandLine);
     configurations.addAll(optionsParser.parse(arguments));
   }
 
   if (configurations != null || configurations.length > 0) {
     testConfigurations(configurations);
   }
 }