Switch polymer's build.dart to use the new linter. This CL does the following

pkg/polymer/test/build/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 'dart:async';
-import 'dart:io';
-
-import 'package:csslib/visitor.dart';
-import 'package:html5lib/dom.dart';
-import 'package:html5lib/parser.dart';
-import 'package:polymer/src/analyzer.dart';
-import 'package:polymer/src/compiler.dart';
-import 'package:polymer/src/file_system.dart';
-import 'package:polymer/src/info.dart';
-import 'package:polymer/src/messages.dart';
-import 'package:polymer/src/compiler_options.dart';
-import 'package:polymer/src/files.dart';
-import 'package:polymer/src/utils.dart';
-
-
-Document parseDocument(String html) => parse(html);
-
-Element parseSubtree(String html) => parseFragment(html).nodes[0];
-
-FileInfo analyzeDefinitionsInTree(Document doc, Messages messages,
-    {String packageRoot: 'packages'}) {
-
-  return analyzeDefinitions(new GlobalInfo(), new UrlInfo('', '', null),
-      doc, packageRoot, messages);
-}
-
-/** Parses files in [fileContents], with [mainHtmlFile] being the main file. */
-List<SourceFile> parseFiles(Map<String, String> fileContents,
-    [String mainHtmlFile = 'index.html']) {
-
-  var result = <SourceFile>[];
-  fileContents.forEach((filename, contents) {
-    var src = new SourceFile(filename);
-    src.document = parse(contents);
-    result.add(src);
-  });
-
-  return result;
-}
-
-/** Analyze all files. */
-Map<String, FileInfo> analyzeFiles(List<SourceFile> files,
-    {Messages messages, String packageRoot: 'packages'}) {
-  messages = messages == null ? new Messages.silent() : messages;
-  var result = new Map<String, FileInfo>();
-
-  // analyze definitions
-  var global = new GlobalInfo();
-  for (var file in files) {
-    var path = file.path;
-    result[path] = analyzeDefinitions(global, new UrlInfo(path, path, null),
-        file.document, packageRoot, messages);
-  }
-
-  // analyze file contents
-  var uniqueIds = new IntIterator();
-  var pseudoElements = new Map();
-  for (var file in files) {
-    analyzeFile(file, result, uniqueIds, pseudoElements, messages, true);
-  }
-  return result;
-}
-
-Compiler createCompiler(Map files, Messages messages, {bool errors: false,
-    bool scopedCss: false}) {
-  List baseOptions = ['--no-colors', '-o', 'out', '--deploy', 'index.html'];
-  if (errors) baseOptions.insert(0, '--warnings_as_errors');
-  if (scopedCss) baseOptions.insert(0, '--scoped-css');
-  var options = CompilerOptions.parse(baseOptions);
-  var fs = new MockFileSystem(files);
-  return new Compiler(fs, options, messages);
-}
-
-String prettyPrintCss(StyleSheet styleSheet) =>
-    ((new CssPrinter())..visitTree(styleSheet)).toString();
-
-/**
- * Abstraction around file system access to work in a variety of different
- * environments.
- */
-class MockFileSystem extends FileSystem {
-  final Map _files;
-  final Map readCount = {};
-
-  MockFileSystem(this._files);
-
-  Future readTextOrBytes(String filename) => readText(filename);
-
-  Future<String> readText(String path) {
-    readCount[path] = readCount.putIfAbsent(path, () => 0) + 1;
-    var file = _files[path];
-    if (file != null) {
-      return new Future.value(file);
-    } else {
-      return new Future.error(
-          new FileException('MockFileSystem: $path not found'));
-    }
-  }
-
-  // Compiler doesn't call these
-  void writeString(String outfile, String text) {}
-  Future flush() {}
-}