pkg/csslib: fixed analysis error, more cleanup

pkg/csslib/test/testing.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.
 
 /** Common definitions used for setting up the test environment. */
 library testing;
 
 import 'package:csslib/parser.dart';
 import 'package:csslib/visitor.dart';
 import 'package:csslib/src/messages.dart';
 
 void useMockMessages() {
   messages = new Messages(printHandler: (message) {});
 }
 
 /**
  * Spin-up CSS parser in checked mode to detect any problematic CSS.  Normally,
  * CSS will allow any property/value pairs regardless of validity; all of our
  * tests (by default) will ensure that the CSS is really valid.
  */
-StyleSheet parseCss(String cssInput, {List errors, List opts}) =>
+StyleSheet parseCss(String cssInput, {List<Message> errors,
+  List<String> opts}) =>
   parse(cssInput, errors: errors, options: opts == null ?
       ['--no-colors', '--checked', '--warnings_as_errors', 'memory'] : opts);
 
 /**
  * Spin-up CSS parser in checked mode to detect any problematic CSS.  Normally,
  * CSS will allow any property/value pairs regardless of validity; all of our
  * tests (by default) will ensure that the CSS is really valid.
  */
-StyleSheet compileCss(String cssInput, {List errors, List opts,
+StyleSheet compileCss(String cssInput, {List<Message> errors, List<String> opts,
     bool polyfill: false, List<StyleSheet> includes: null}) =>
   compile(cssInput, errors: errors, options: opts == null ?
       ['--no-colors', '--checked', '--warnings_as_errors', 'memory'] : opts,
       polyfill: polyfill, includes: includes);
 
-StyleSheet polyFillCompileCss(input, {List errors, List opts}) =>
+StyleSheet polyFillCompileCss(input, {List<Message> errors,
+  List<String> opts}) =>
     compileCss(input, errors: errors, polyfill: true, opts: opts);
 
 /** CSS emitter walks the style sheet tree and emits readable CSS. */
 final _emitCss = new CssPrinter();
 
 /** Simple Visitor does nothing but walk tree. */
 final _cssVisitor = new Visitor();
 
 /** Pretty printer for CSS. */
 String prettyPrint(StyleSheet ss) {
@@ skipping 11 matching lines @@
   walkTree(ss);
   return (_emitCss..visitTree(ss, pretty: false)).toString();
 }
 
 /** Walks the style sheet tree does nothing; insures the basic walker works. */
 void walkTree(StyleSheet ss) {
   _cssVisitor..visitTree(ss);
 }
 
 String dumpTree(StyleSheet ss) => treeToDebugString(ss);