Rework contribution sorter to use futures

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/plugin/protocol/protocol.dart' as protocol
     show Element, ElementKind;
 import 'package:analysis_server/plugin/protocol/protocol.dart'
     hide Element, ElementKind;
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/provisional/completion/dart/completion_target.dart';
-import 'package:analysis_server/src/services/completion/common_usage_computer.dart';
 import 'package:analysis_server/src/services/completion/completion_manager.dart';
+import 'package:analysis_server/src/services/completion/dart/common_usage_sorter.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_cache.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
 import 'package:analysis_server/src/services/completion/imported_reference_contributor.dart';
 import 'package:analysis_server/src/services/completion/prefixed_element_contributor.dart';
 import 'package:analysis_server/src/services/index/index.dart';
 import 'package:analysis_server/src/services/index/local_memory_index.dart';
 import 'package:analysis_server/src/services/search/search_engine_internal.dart';
 import 'package:analyzer/src/generated/ast.dart';
 import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
@@ skipping 407 matching lines @@
       assertSuggestGetter(name, returnType);
       assertSuggestSetter(name);
     } else {
       assertNotSuggested(name);
     }
   }
 
   bool computeFast() {
     expect(computeFastResult, isNull);
     _completionManager = new DartCompletionManager(context, searchEngine,
-        testSource, cache, [contributor], new CommonUsageComputer({}));
+        testSource, cache, [contributor], new CommonUsageSorter({}));
     var result =
         _completionManager.computeFast(request, new CompletionPerformance());
     expect(request.replacementOffset, isNotNull);
     expect(request.replacementLength, isNotNull);
     computeFastResult = result.isEmpty;
     return computeFastResult;
   }
 
   Future computeFull(assertFunction(bool result), {bool fullAnalysis: true}) {
     if (computeFastResult == null) {
@@ skipping 4265 matching lines @@
       assertNotSuggested('bar2');
       assertNotSuggested('_B');
       assertSuggestLocalClass('Y');
       assertSuggestLocalClass('C');
       assertSuggestLocalVariable('f', null);
       assertNotSuggested('x');
       assertNotSuggested('e');
     });
   }
 }