Mirrors overhaul.

dart/tests/compiler/dart2js_extra/mirror_invalid_invoke_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 we cannot reflect on elements not covered by the `MirrorsUsed`
 // annotation.
 
 library test;
 
 @MirrorsUsed(targets: 'foo')
 import 'dart:mirrors';
 
 import 'package:expect/expect.dart';
 
 import '../../language/compiler_annotations.dart';
 
 foo() => 1;
 
 @DontInline
 // Use a closure to prevent inlining until the annotation is implemented.
 bar() => () => 2;
 
 main() {
   bar();  // Call bar, so it is included in the program.
 
-  var lm = currentMirrorSystem().findLibrary(const Symbol('test')).single;
+  var lm = currentMirrorSystem().findLibrary(const Symbol('test'));
   Expect.equals(1, lm.invoke(const Symbol('foo'), []).reflectee);
   Expect.throws(() => lm.invoke(const Symbol('bar'),  []));
 }