Add mirrors tests

test/codegen/lib/mirrors/syntax_error_test.dart

+// Copyright (c) 2013, 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.
+
+// Regression test for Issue 15744
+// Also, tests that syntax errors in reflected classes are reported correctly.
+
+import 'dart:mirrors';
+
+class MD {
+  final String name;
+  const MD({this.name});
+}
+
+@MD(name:'A')
+class A {}
+
+@MD(name:'B')
+class B {
+  static x = { 0: 0; };  /// 01: compile-time error
+}
+
+main() {
+  reflectClass(A).metadata;
+  reflectClass(B).newInstance(const Symbol(''), []);
+}