Add an analysis option to disable cache flushing.

pkg/analyzer/test/src/context/cache_test.dart

Index: pkg/analyzer/test/src/context/cache_test.dart
diff --git a/pkg/analyzer/test/src/context/cache_test.dart b/pkg/analyzer/test/src/context/cache_test.dart
index d6af6ce666d657006f221194fc8f6e43a24f2d88..44f609549cec0f8de3d3077888ef000049dd635a 100644
--- a/pkg/analyzer/test/src/context/cache_test.dart
+++ b/pkg/analyzer/test/src/context/cache_test.dart
@@ -1287,7 +1287,10 @@ class UniversalCachePartitionTest extends CachePartitionTest {
 }
 
 class _InternalAnalysisContextMock extends TypedMock
-    implements InternalAnalysisContext {}
+    implements InternalAnalysisContext {
+  @override
+  final AnalysisOptions analysisOptions = new AnalysisOptionsImpl();
+}
 
 /**
  * Keep the given [keepDescriptor], invalidate all the other results.