Added polyfill for var (moved from web_ui)

pkg/csslib/test/var_test.dart

 // Copyright (c) 2013, 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 var_test;
 
 import 'package:unittest/unittest.dart';
 import 'package:csslib/parser.dart';
 import 'package:csslib/visitor.dart';
 import 'testing.dart';
@@ skipping 605 matching lines @@
   expect(prettyPrint(stylesheet), generated2);
 
   stylesheet = compileCss(input2, errors: errors..clear(),
       opts: ['--no-colors', 'memory', '--no-less']);
 
   expect(stylesheet != null, true);
   expect(errors.isEmpty, true, reason: errors.toString());
   expect(prettyPrint(stylesheet), generated2);
 }
 
+void polyfill() {
+  var errors = [];
+  var input = r'''
+@color-background: red;
+@color-foreground: blue;
+.test {
+  background-color: @color-background;
+  color: @color-foreground;
+}''';
+
+  var generated = r'''.test {
+  background-color: #f00;
+  color: #00f;
+}''';
+
+  var stylesheet = compileCss(input, errors: errors,
+      opts: ['--no-colors', 'memory'], polyfill: true);
+
+  expect(stylesheet != null, true);
+  expect(errors.isEmpty, true, reason: errors.toString());
+  expect(prettyPrint(stylesheet), generated);
+}
+
+
+
 main() {
   test('Simple var', simpleVar);
   test('Expressions var', expressionsVar);
   test('Default value in var()', defaultVar);
   test('CSS Parser only var', parserVar);
   test('Var syntax', testVar);
   test('Cycles var', cyclesVar);
   test('Less syntax', testLess);
+  test('Polyfill', polyfill);
 }