Remove warnings from dart2js test-suite.

tests/compiler/dart2js/mirror_helper_unique_minification_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.
 
 import "package:expect/expect.dart";
 import 'dart:async';
 import "package:async_helper/async_helper.dart";
 import 'memory_compiler.dart' show compilerFor;
 import '../../../sdk/lib/_internal/compiler/implementation/apiimpl.dart' show
     Compiler;
 import
     '../../../sdk/lib/_internal/compiler/implementation/dart_backend/dart_backend.dart'
 show
     DartBackend;
 import
     '../../../sdk/lib/_internal/compiler/implementation/tree/tree.dart'
-show
-    Node, Identifier;
+show Identifier, Node, Send;
 import
     '../../../sdk/lib/_internal/compiler/implementation/mirror_renamer/mirror_renamer.dart'
 show
     MirrorRenamer;
 
 main() {
   testUniqueMinification();
   testNoUniqueMinification();
 }
 
@@ skipping 17 matching lines @@
     Map<Node, String> renames = backend.renames;
     Map<String, String> symbols = mirrorRenamer.symbols;
 
     // Check that no two different source code names get the same mangled name,
     // with the exception of MirrorSystem.getName that gets renamed to the same
     // mangled name as the getNameHelper from _mirror_helper.dart.
     for (Node node in renames.keys) {
       Identifier identifier = node.asIdentifier();
       if (identifier != null) {
         String source = identifier.source;
-        if (mirrorRenamer.mirrorSystemGetNameNodes.first.selector == node)
+        Send send = mirrorRenamer.mirrorSystemGetNameNodes.first;
+        if (send.selector == node)
           continue;
         if (symbols.containsKey(renames[node])) {
           print(node);
           Expect.equals(source, symbols[renames[node]]);
         }
       }
     }
   }));
 }
 
@@ skipping 17 matching lines @@
   noSuchMethod(invocation) {
     MirrorSystem.getName(null);
   }
 }
 
 main() {
   new Foo().fisk();
   var hest;
 }
 """};