Remove uses of unittest in the HTML tests where possible.

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

-library XSLTProcessorTest;
-import 'package:unittest/unittest.dart';
-import 'package:unittest/html_individual_config.dart';
 import 'dart:html';
 
+import 'package:expect/minitest.dart';
+
 main() {
-
-  useHtmlIndividualConfiguration();
-
   group('supported', () {
     test('supported', () {
       expect(XsltProcessor.supported, true);
     });
   });
 
   group('functional', () {
     var isXsltProcessor =
       predicate((x) => x is XsltProcessor, 'is an XsltProcessor');
 
     var expectation = XsltProcessor.supported ? returnsNormally : throws;
 
     test('constructorTest', () {
       expect(() {
         var processor = new XsltProcessor();
         expect(processor, isNotNull);
         expect(processor, isXsltProcessor);
       }, expectation);
     });
   });
 
 }