Add mirrors tests

test/codegen/lib/mirrors/regress_14304_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.
 
-// Test that the type argument is available inside a closure.
+// Regression test for Issue 14304.
 
+import "dart:mirrors";
 import "package:expect/expect.dart";
 
 class A<T> {
-  foo() {
-    bar() => T;
-    return bar();
-  }
+  T m() {}
 }
 
 main() {
-  Expect.equals(new A<int>().foo(), int);
-}
+  ClassMirror a = reflectClass(A);
+  TypeVariableMirror t = a.typeVariables[0];
+  MethodMirror m = a.declarations[#m];
+  
+  Expect.equals(t, m.returnType);
+}