Remove uses of unittest in the HTML tests where possible.

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

-library PerformanceApiTest;
-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(Performance.supported, true);
     });
   });
 
   group('performance', () {
     test('PerformanceApi', () {
       // Check that code below will not throw exceptions if supported.
       var expectation = Performance.supported ? returnsNormally : throws;
       expect(() {
         var requestStart = window.performance.timing.requestStart;
         var responseStart = window.performance.timing.responseStart;
         var responseEnd = window.performance.timing.responseEnd;
 
         var loading = window.performance.timing.domLoading;
         var loadedStart = window.performance.timing.domContentLoadedEventStart;
         var loadedEnd = window.performance.timing.domContentLoadedEventEnd;
         var complete = window.performance.timing.domComplete;
 
         var loadEventStart = window.performance.timing.loadEventStart;
       }, expectation);
     });
   });
 }