remove CompletionCache and obsolete tests, and cleanup imports

pkg/analysis_server/test/services/completion/completion_manager_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.services.completion.manager;
-
-import 'package:analysis_server/src/services/completion/completion_manager.dart';
-import 'package:analysis_server/src/services/completion/dart_completion_manager.dart';
-import 'package:analyzer/src/generated/source.dart';
-import 'package:test_reflective_loader/test_reflective_loader.dart';
-import 'package:unittest/unittest.dart';
-
-import '../../abstract_context.dart';
-import '../../utils.dart';
-
-main() {
-  initializeTestEnvironment();
-  defineReflectiveTests(CompletionManagerTest);
-}
-
-@reflectiveTest
-class CompletionManagerTest extends AbstractContextTest {
-  var perf = new CompletionPerformance();
-
-  test_dart() {
-    Source source = addSource('/does/not/exist.dart', '');
-    var manager = new CompletionManager.create(context, source, null, []);
-    expect(manager.runtimeType, DartCompletionManager);
-  }
-
-  test_html() {
-    Source source = addSource('/does/not/exist.html', '');
-    var manager = new CompletionManager.create(context, source, null, []);
-    expect(manager.runtimeType, NoOpCompletionManager);
-  }
-
-  test_null_context() {
-    Source source = addSource('/does/not/exist.dart', '');
-    var manager = new CompletionManager.create(null, source, null, []);
-    expect(manager.runtimeType, NoOpCompletionManager);
-  }
-
-  test_other() {
-    Source source = addSource('/does/not/exist.foo', '');
-    var manager = new CompletionManager.create(context, source, null, []);
-    expect(manager.runtimeType, NoOpCompletionManager);
-  }
-}