Move minitest.dart into the expect package.

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

 import 'dart:html';
 
-import 'package:minitest/minitest.dart';
+import 'package:expect/minitest.dart';
 
 main() {
   group('supported', () {
     test('supported', () {
       expect(ApplicationCache.supported, isTrue);
     });
   });
 
   group('ApplicationCache', () {
     test('ApplicationCache', () {
@@ skipping 17 matching lines @@
     case ApplicationCache.DOWNLOADING: // DOWNLOADING == 3
       return 'DOWNLOADING';
     case ApplicationCache.UPDATEREADY:  // UPDATEREADY == 4
       return 'UPDATEREADY';
     case ApplicationCache.OBSOLETE: // OBSOLETE == 5
       return 'OBSOLETE';
     default:
       return 'UNKNOWN CACHE STATUS';
   };
 }