fix combinator contributor

pkg/analysis_server/test/services/completion/dart/completion_contributor_util.dart

 // Copyright (c) 2014, 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.
 
 library test.services.completion.dart.util;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart' as protocol
     show Element, ElementKind;
@@ skipping 197 matching lines @@
     //    expect(param[0], equals('('));
     //    expect(param[param.length - 1], equals(')'));
     expect(element.returnType,
         equals(returnType != null ? returnType : 'dynamic'));
     // TODO (danrubel) Determine why param info is missing
     //    assertHasParameterInfo(cs);
     return cs;
   }
 
   CompletionSuggestion assertSuggestTopLevelVar(String name, String returnType,
-      [int relevance = DART_RELEVANCE_DEFAULT,
-      CompletionSuggestionKind kind = CompletionSuggestionKind.INVOCATION,
-      String importUri]) {
+      {int relevance: DART_RELEVANCE_DEFAULT,
+      CompletionSuggestionKind kind: CompletionSuggestionKind.INVOCATION,
+      String importUri}) {
     CompletionSuggestion cs = assertSuggest(name,
         csKind: kind, relevance: relevance, importUri: importUri);
     expect(cs.returnType, returnType != null ? returnType : 'dynamic');
     protocol.Element element = cs.element;
     expect(element, isNotNull);
     expect(element.kind, equals(protocol.ElementKind.TOP_LEVEL_VARIABLE));
     expect(element.name, equals(name));
     expect(element.parameters, isNull);
     expect(element.returnType, returnType != null ? returnType : 'dynamic');
     assertHasNoParameterInfo(cs);
@@ skipping 100 matching lines @@
   }
 
   @override
   void setUp() {
     super.setUp();
     index = createLocalMemoryIndex();
     searchEngine = new SearchEngineImpl(index);
     contributor = createContributor();
   }
 }