Add supported checks to the SVG library, and library cleanup.

tests/html/svgelement2_test.dart

Index: tests/html/svgelement2_test.dart
diff --git a/tests/html/svgelement2_test.dart b/tests/html/svgelement2_test.dart
deleted file mode 100644
index 468b61a4016f857e97e3428c6fc66fd87b0146f9..0000000000000000000000000000000000000000
--- a/tests/html/svgelement2_test.dart
+++ /dev/null
@@ -1,21 +0,0 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library SVGElement2Test;
-import '../../pkg/unittest/lib/unittest.dart';
-import '../../pkg/unittest/lib/html_config.dart';
-import 'svgelement_test.dart' as originalTest;
-
-class A {
-  var _this;
-  A(x) : this._this = x;
-}
-
-main() {
-  // The svgelement_test requires the field "_this" to map to "_this". In this
-  // test-case we use another library's '_this' first (see issue 3039 and
-  // _ChildNodeListLazy.first).
-  expect(new A(499)._this, 499);
-  originalTest.main();
-}