Adding supported checks to media events

tests/html/media_stream_test.dart

Index: tests/html/media_stream_test.dart
diff --git a/tests/html/media_stream_test.dart b/tests/html/media_stream_test.dart
index 1e97511a617e1549c68c168b2f451d9fb935fe88..dc4d2ec1e4210873782a18ee67d90736d4c94b3e 100644
--- a/tests/html/media_stream_test.dart
+++ b/tests/html/media_stream_test.dart
@@ -16,6 +16,34 @@ main() {
     });
   });
 
-  // No additional tests right now since this API prompts for user input to
-  // continue.
+  group('supported_MediaStreamEvent', () {
+    test('supported', () {
+      expect(MediaStreamEvent.supported, true);
+    });
+  });
+
+  group('supported_MediaStreamTrackEvent', () {
+    test('supported', () {
+      expect(MediaStreamTrackEvent.supported, true);
+    });
+  });
+
+  group('constructors', () {
+    test('MediaStreamEvent', () {
+      var expectation = MediaStreamEvent.supported ? returnsNormally : throws;
+      expect(() {
+        var event = document.$dom_createEvent('MediaStreamEvent');
+        expect(event is MediaStreamEvent, isTrue);
+      }, expectation);
+    });
+
+    test('MediaStreamTrackEvent', () {
+      var expectation =
+          MediaStreamTrackEvent.supported ? returnsNormally : throws;
+      expect(() {
+        var event = document.$dom_createEvent('MediaStreamTrackEvent');
+        expect(event is MediaStreamTrackEvent, isTrue);
+      }, expectation);
+    });
+  });
 }