Add Supported class to dart:html

tests/html/typed_arrays_1_test.dart

Index: tests/html/typed_arrays_1_test.dart
diff --git a/tests/html/typed_arrays_1_test.dart b/tests/html/typed_arrays_1_test.dart
index 12bd9f6aae58b8b94972154365b747829e975c69..52cd41b282e6569dece7c7bf7a01c7d0cb15ea96 100644
--- a/tests/html/typed_arrays_1_test.dart
+++ b/tests/html/typed_arrays_1_test.dart
@@ -12,11 +12,11 @@ main() {
 
   var isnumList = predicate((x) => x is List<num>, 'is a List<num>');
   var isStringList = predicate((x) => x is List<String>, 'is a List<String>');
-  var expectation = ArrayBuffer.supported ? returnsNormally : throws;
+  var expectation = Platform.supportsTypedData ? returnsNormally : throws;
 
   group('supported', () {
     test('supported', () {
-      expect(ArrayBuffer.supported, true);
+      expect(Platform.supportsTypedData, true);
     });
   });