Fixed single quote escaping

pkg/csslib/test/compiler_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.
 
 library compiler_test;
 
 import 'dart:convert';
 import 'package:unittest/unittest.dart';
 import 'package:csslib/parser.dart';
 import 'package:csslib/visitor.dart';
@@ skipping 573 matching lines @@
 div:nth-child(2n) { color : red; }
 ''';
 
   var stylesheet = parseCss(input, errors: errors,
       opts: ['--no-colors', 'memory']);
 
   expect(stylesheet != null, true);
   expect(errors.isEmpty, true, reason: errors.toString());
   expect(prettyPrint(stylesheet), r'''
 html:lang(fr-ca) {
-  quotes: "\" " " \"";
+  quotes: '" ' ' "';
 }
 zoom {
 }
 a:link {
   color: #f00;
 }
 :link {
   color: #00f;
 }
 a:focus {
@@ skipping 114 matching lines @@
   test('Selector Groups', testSelectorGroups);
   test('Combinator', testCombinator);
   test('Wildcards', testWildcard);
   test('Pseudo', testPseudo);
   test('Attributes', testAttribute);
   test('Negation', testNegation);
   test('@host', testHost);
   test('Parse List<int> as input', testArrayOfChars);
   test('Simple Emitter', testEmitter);
 }