remove CompletionCache and obsolete tests, and cleanup imports

pkg/analysis_server/test/domain_completion_test.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.domain.completion;
 
 import 'dart:async';
 
 import 'package:analysis_server/plugin/protocol/protocol.dart';
 import 'package:analysis_server/src/analysis_server.dart';
 import 'package:analysis_server/src/channel/channel.dart';
 import 'package:analysis_server/src/constants.dart';
 import 'package:analysis_server/src/context_manager.dart';
 import 'package:analysis_server/src/domain_analysis.dart';
 import 'package:analysis_server/src/domain_completion.dart';
 import 'package:analysis_server/src/plugin/server_plugin.dart';
 import 'package:analysis_server/src/provisional/completion/completion_core.dart'
     show AnalysisRequest, CompletionRequest, CompletionResult;
+import 'package:analysis_server/src/provisional/completion/dart/completion_dart.dart';
 import 'package:analysis_server/src/services/completion/completion_manager.dart';
 import 'package:analysis_server/src/services/completion/dart/contribution_sorter.dart';
 import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
 import 'package:analysis_server/src/services/index/index.dart' show Index;
 import 'package:analysis_server/src/services/index/local_memory_index.dart';
 import 'package:analysis_server/src/services/search/search_engine.dart';
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/instrumentation/instrumentation.dart';
 import 'package:analyzer/source/pub_package_map_provider.dart';
 import 'package:analyzer/src/generated/engine.dart';
@@ skipping 757 matching lines @@
       expect(replacementLength, equals(4));
       // Suggestions based upon imported elements are partially filtered
       //assertHasResult(CompletionSuggestionKind.INVOCATION, 'Object');
       assertHasResult(CompletionSuggestionKind.INVOCATION, 'test',
           relevance: DART_RELEVANCE_LOCAL_TOP_LEVEL_VARIABLE);
       assertNoResult('HtmlElement');
     });
   }
 }
 
-class MockCache extends CompletionCache {
-  MockCache(AnalysisContext context, Source source) : super(context, source);
-}
-
 class MockCompletionManager implements CompletionManager {
   final AnalysisContext context;
   final Source source;
   final SearchEngine searchEngine;
   StreamController<CompletionResult> controller;
   int computeCallCount = 0;
   int disposeCallCount = 0;
 
   MockCompletionManager(this.context, this.source, this.searchEngine);
 
@@ skipping 179 matching lines @@
 }
     ''');
     await waitForTasksFinished();
     Request request =
         new CompletionGetSuggestionsParams(testFile, 0).toRequest('0');
     Response response = handler.handleRequest(request);
     expect(response.error, isNotNull);
     expect(response.error.code, RequestErrorCode.NO_INDEX_GENERATED);
   }
 }