Add an analysis option to disable cache flushing.

pkg/analyzer/test/src/task/dart_work_manager_test.dart

Index: pkg/analyzer/test/src/task/dart_work_manager_test.dart
diff --git a/pkg/analyzer/test/src/task/dart_work_manager_test.dart b/pkg/analyzer/test/src/task/dart_work_manager_test.dart
index 12388d086ccf26360bd2272d085eaf6cadfe95b5..2927305eaf7309702e96c1a7df8e0567195e7a4c 100644
--- a/pkg/analyzer/test/src/task/dart_work_manager_test.dart
+++ b/pkg/analyzer/test/src/task/dart_work_manager_test.dart
@@ -12,6 +12,8 @@ import 'package:analyzer/src/dart/scanner/scanner.dart' show ScannerErrorCode;
 import 'package:analyzer/src/generated/engine.dart'
     show
         AnalysisErrorInfoImpl,
+        AnalysisOptions,
+        AnalysisOptionsImpl,
         CacheState,
         ChangeNoticeImpl,
         InternalAnalysisContext;
@@ -827,6 +829,9 @@ class _InternalAnalysisContextMock extends TypedMock
   Map<Source, ChangeNoticeImpl> _pendingNotices = <Source, ChangeNoticeImpl>{};
 
   @override
+  final AnalysisOptions analysisOptions = new AnalysisOptionsImpl();
+
+  @override
   final ReentrantSynchronousStream<InvalidatedResult> onResultInvalidated =
       new ReentrantSynchronousStream<InvalidatedResult>();