Move minitest.dart into the expect package.

pkg/dev_compiler/test/codegen/lib/html/js_util_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.
 
 @JS()
 library js_native_test;
 
 import 'dart:async';
 import 'dart:html';
 import 'dart:typed_data' show ByteBuffer, Int32List;
 import 'dart:indexed_db' show IdbFactory, KeyRange;
 
 import 'package:js/js.dart';
 import 'package:js/js_util.dart' as js_util;
-import 'package:minitest/minitest.dart';
+import 'package:expect/minitest.dart';
 
 _injectJs() {
   final script = new ScriptElement();
   script.type = 'text/javascript';
   script.innerHtml = r"""
 var x = 42;
 
 var _x = 123;
 
 var myArray = ["value1"];
@@ skipping 308 matching lines @@
       expect(textNode is Text, isTrue);
       expect(textNode.text, equals('foo'));
     });
 
     test('typed object', () {
       Foo f = js_util.callConstructor(JSFooType, [42]);
       expect(f.a, equals(42));
     });
   });
 }