refactor library prefix suggestion generation

pkg/analysis_server/test/services/completion/completion_test_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.util;
 
 import 'dart:async';
 
 import 'package:analysis_server/src/protocol.dart' as protocol show Element,
     ElementKind;
@@ skipping 125 matching lines @@
     return cs;
   }
 
   CompletionSuggestion assertSuggestLibraryPrefix(String prefix,
       [CompletionRelevance relevance = CompletionRelevance.DEFAULT]) {
     CompletionSuggestion cs =
         assertSuggest(CompletionSuggestionKind.LIBRARY_PREFIX, prefix, relevance);
     protocol.Element element = cs.element;
     expect(element, isNotNull);
     expect(element.kind, equals(protocol.ElementKind.LIBRARY));
-    expect(element.name, equals(prefix));
     expect(element.returnType, isNull);
     return cs;
   }
 
   CompletionSuggestion assertSuggestLocalVariable(String name,
       String returnType, [CompletionRelevance relevance =
       CompletionRelevance.DEFAULT]) {
     CompletionSuggestion cs =
         assertSuggest(CompletionSuggestionKind.LOCAL_VARIABLE, name, relevance);
     expect(cs.returnType, equals(returnType));
@@ skipping 153 matching lines @@
       sb.write('\n  in');
       AstNode node = completionNode;
       while (node != null) {
         sb.write('\n    ${node.runtimeType}');
         node = node.parent;
       }
     }
     fail(sb.toString());
   }
 }