Rework contribution sorter to use futures

pkg/analysis_server/lib/src/services/completion/contribution_sorter.dart

Index: pkg/analysis_server/lib/src/services/completion/contribution_sorter.dart
diff --git a/pkg/analysis_server/lib/src/services/completion/contribution_sorter.dart b/pkg/analysis_server/lib/src/services/completion/contribution_sorter.dart
deleted file mode 100644
index dbf995b4114f48b8c1b6912ef8033d236295726f..0000000000000000000000000000000000000000
--- a/pkg/analysis_server/lib/src/services/completion/contribution_sorter.dart
+++ /dev/null
@@ -1,26 +0,0 @@
-// 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 services.completion.sorter;
-
-import 'package:analysis_server/plugin/protocol/protocol.dart';
-import 'package:analysis_server/src/provisional/completion/completion_core.dart';
-
-/**
- * The abstract class `ContributionSorter` defines the behavior of objects
- * that are used to adjust the relevance of an existing list of suggestions.
- * This is a long-lived object that should not maintain state between
- * calls to it's [sort] method.
- */
-abstract class ContributionSorter {
-  /**
-   * After [CompletionSuggestion]s have been computed,
-   * this method is called to adjust the relevance of those suggestions.
-   * Return an [AnalysisRequest] if more analysis is needed,
-   * or `null` if suggestion sorting is complete.
-   * This method should execute quickly and not block.
-   */
-  AnalysisRequest sort(
-      CompletionRequest request, Iterable<CompletionSuggestion> suggestions);
-}