Hide inference hints. Fixes #24563.

pkg/analyzer/test/src/task/strong/strong_test_helper.dart

Index: pkg/analyzer/test/src/task/strong/strong_test_helper.dart
diff --git a/pkg/analyzer/test/src/task/strong/strong_test_helper.dart b/pkg/analyzer/test/src/task/strong/strong_test_helper.dart
index 604d561c35198ae618907bfb30540b15e1f6bf2b..ea5c52e1da866a611b121a851e302b4e54002aad 100644
--- a/pkg/analyzer/test/src/task/strong/strong_test_helper.dart
+++ b/pkg/analyzer/test/src/task/strong/strong_test_helper.dart
@@ -63,6 +63,7 @@ void testChecker(String name, Map<String, String> testFiles) {
     AnalysisEngine.instance.useTaskModel = true;
     var context = AnalysisEngine.instance.createAnalysisContext();
     context.analysisOptions.strongMode = true;
+    context.analysisOptions.strongModeHints = true;
 
     context.sourceFactory = new SourceFactory([
       new MockDartSdk(mockSdkSources, reportMissing: true).resolver,