move combinator contributor to new task model

pkg/analysis_server/lib/src/services/completion/combinator_contributor.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 services.completion.contributor.dart.combinator;
-
-import 'dart:async';
-
-import 'package:analysis_server/src/protocol_server.dart'
-    hide Element, ElementKind;
-import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
-import 'package:analysis_server/src/services/completion/suggestion_builder.dart';
-import 'package:analyzer/src/generated/ast.dart';
-import 'package:analyzer/src/generated/element.dart';
-
-/**
- * A contributor for calculating `completion.getSuggestions` request results
- * for the import combinators show and hide.
- */
-class CombinatorContributor extends DartCompletionContributor {
-  _CombinatorSuggestionBuilder builder;
-
-  @override
-  bool computeFast(DartCompletionRequest request) {
-    builder = request.target.containingNode
-        .accept(new _CombinatorAstVisitor(request));
-    return builder == null;
-  }
-
-  @override
-  Future<bool> computeFull(DartCompletionRequest request) {
-    if (builder != null) {
-      return builder.execute(request.target.containingNode);
-    }
-    return new Future.value(false);
-  }
-}
-
-/**
- * A visitor for determining which imported classes and top level variables
- * should be suggested and building those suggestions.
- */
-class _CombinatorAstVisitor
-    extends GeneralizingAstVisitor<_CombinatorSuggestionBuilder> {
-  final DartCompletionRequest request;
-
-  _CombinatorAstVisitor(this.request);
-
-  @override
-  _CombinatorSuggestionBuilder visitCombinator(Combinator node) {
-    return new _CombinatorSuggestionBuilder(
-        request, CompletionSuggestionKind.IDENTIFIER);
-  }
-
-  @override
-  _CombinatorSuggestionBuilder visitNode(AstNode node) {
-    return null;
-  }
-}
-
-/**
- * A `_CombinatorSuggestionBuilder` determines which imported classes
- * and top level variables should be suggested and builds those suggestions.
- * This operation is instantiated during `computeFast`
- * and calculates the suggestions during `computeFull`.
- */
-class _CombinatorSuggestionBuilder extends LibraryElementSuggestionBuilder {
-  _CombinatorSuggestionBuilder(
-      DartCompletionRequest request, CompletionSuggestionKind kind)
-      : super(request, kind, false, false);
-
-  Future<bool> execute(AstNode node) {
-    var directive = node.getAncestor((parent) => parent is NamespaceDirective);
-    if (directive is NamespaceDirective) {
-      LibraryElement library = directive.uriElement;
-      if (library != null) {
-        library.visitChildren(this);
-      }
-    }
-    return new Future.value(false);
-  }
-}