Update mirror tests for removed API.

tests/lib/mirrors/to_string_test.dart

Index: tests/lib/mirrors/to_string_test.dart
diff --git a/tests/lib/mirrors/to_string_test.dart b/tests/lib/mirrors/to_string_test.dart
index b553caa6cd83f6fbc029cf9601ff6681fe63cb9c..8344bc4de7fa245445f2b7bd9b7af4b832f6c6eb 100644
--- a/tests/lib/mirrors/to_string_test.dart
+++ b/tests/lib/mirrors/to_string_test.dart
@@ -24,8 +24,9 @@ main() {
   expect("InstanceMirror on 1", reflect(1));
   expect("ClassMirror on 'Foo'", reflectClass(Foo));
   expect("VariableMirror on 'field'",
-         reflectClass(Foo).variables.values.single);
-  expect("MethodMirror on 'method'", reflectClass(Foo).methods.values.single);
+         reflectClass(Foo).declarations[#field]);
+  expect("MethodMirror on 'method'",
+         reflectClass(Foo).declarations[#method]);
   String s = reflect(main).toString();
   Expect.isTrue(s.startsWith("ClosureMirror on '"), s);
 }