Move minitest.dart into the expect package.

pkg/dev_compiler/test/codegen/lib/html/fontface_test.dart

 // Copyright (c) 2015, 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.
 
 import 'dart:html';
 
-import 'package:minitest/minitest.dart';
+import 'package:expect/minitest.dart';
 
 main() {
   test("Creation with parameters", () {
     var font =
         new FontFace('Ahem', 'url(Ahem.ttf)', {'variant': 'small-caps'});
     expect(font is FontFace, isTrue);
     expect(font.family, 'Ahem');
     expect(font.variant, 'small-caps');
   });
 }