Move minitest.dart into the expect package.

pkg/dev_compiler/test/codegen/lib/html/canvas_pixel_array_type_alias_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
 
 import 'dart:html';
 import 'dart:typed_data';
 
-import 'package:minitest/minitest.dart';
+import 'package:expect/minitest.dart';
 
 // We have aliased the legacy type CanvasPixelArray with the new type
 // Uint8ClampedArray by mapping the CanvasPixelArray type tag to
 // Uint8ClampedArray.  It is not a perfect match since CanvasPixelArray is
 // missing the ArrayBufferView members.  These should appear to be null.
 
 var inscrutable;
 
 main() {
   inscrutable = (x) => x;
@@ skipping 87 matching lines @@
     });
   });
 }
 
 void checkPixel(List<int> data, int offset, List<int> rgba) {
   offset *= 4;
   for (var i = 0; i < 4; ++i) {
     expect(rgba[i], equals(data[offset + i]));
   }
 }