Fixing Element.matches to be cross-platform and follow latest spec.

tests/html/element_test.dart

Index: tests/html/element_test.dart
diff --git a/tests/html/element_test.dart b/tests/html/element_test.dart
index 74e38796b71f5a865aee31cafcf505a822741c02..8500c734ebb94124a46fd3f5c7cd43edf1f5aaed 100644
--- a/tests/html/element_test.dart
+++ b/tests/html/element_test.dart
@@ -646,6 +646,17 @@ main() {
     });
   });
 
+  group('matches', () {
+    test('matches', () {
+      var element = new DivElement();
+      element.classes.add('test');
+
+      expect(element.matches('div'), true);
+      expect(element.matches('span'), false);
+      expect(element.matches('.test'), true);
+    });
+  });
+
   group('queryAll', () {
     List<Element> getQueryAll() {
       return new Element.html("""