Remove warnings from dart2js test-suite.

tests/compiler/dart2js/unparser2_test.dart

 // Copyright (c) 2012, 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 "../../../sdk/lib/_internal/compiler/implementation/scanner/scannerlib.dart";
 import "../../../sdk/lib/_internal/compiler/implementation/tree/tree.dart";
 
 import "../../../sdk/lib/_internal/compiler/implementation/dart2jslib.dart"
     show DiagnosticListener,
@@ skipping 65 matching lines @@
     messages = [];
   }
   void internalError(node, String reason) {
     messages.add(reason);
     throw reason;
   }
 
   void log(message) {
     messages.add(message);
   }
+
+  noSuchMethod(Invocation invocation) => throw 'unsupported operation';
 }