Remove warnings from dart2js test-suite.

tests/compiler/dart2js/resolution_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 resolution does not resolve things we know will not be
 // needed by the backend.
 
 import 'package:expect/expect.dart';
 import "package:async_helper/async_helper.dart";
 import 'compiler_helper.dart';
 import 'parser_helper.dart';
+import '../../../sdk/lib/_internal/compiler/implementation/apiimpl.dart';
 
 const String NO_RUNTIME_TYPE = r"""
 import 'dart:core' as prefix;
 class A {
   A();
   A.z();
   static var bar;
   static foo() {}
 }
 main() {
@@ skipping 91 matching lines @@
     Expect.isFalse(compiler.enqueuer.resolution.isProcessed(element));
   });
 
   testHasRuntimeType(HAS_RUNTIME_TYPE_1);
   testHasRuntimeType(HAS_RUNTIME_TYPE_2);
   testHasRuntimeType(HAS_RUNTIME_TYPE_3);
   testHasRuntimeType(HAS_RUNTIME_TYPE_4);
   testHasRuntimeType(HAS_RUNTIME_TYPE_5);
   testHasRuntimeType(HAS_RUNTIME_TYPE_6);
 }