Remove uses of unittest in the HTML tests where possible.

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

-library StorageTest;
-import 'package:unittest/unittest.dart';
-import 'package:unittest/html_config.dart';
 import 'dart:html';
 
+import 'package:expect/minitest.dart';
+
 main() {
-  useHtmlConfiguration();
   test('GetItem', () {
     final value = window.localStorage['does not exist'];
     expect(value, isNull);
   });
   test('SetItem', () {
     final key = 'foo';
     final value = 'bar';
     window.localStorage[key] = value;
     final stored = window.localStorage[key];
     expect(stored, value);
   });
 
   test('event', () {
     // Bug 8076 that not all optional params are optional in Dartium.
     var event = new StorageEvent('something', oldValue: 'old', newValue: 'new',
         url: 'url', key: 'key');
     expect(event is StorageEvent, isTrue);
     expect(event.oldValue, 'old');
     expect(event.newValue, 'new');
   });
 }