expose strong checker API, for use by analyzer_cli

lib/src/checker/rules.dart

Index: lib/src/checker/rules.dart
diff --git a/lib/src/checker/rules.dart b/lib/src/checker/rules.dart
index 72dce22c26348a1332ba5dce4433cf735ff49fdc..09ebb228de7fc76d0355832022896a7a3ee64ae4 100644
--- a/lib/src/checker/rules.dart
+++ b/lib/src/checker/rules.dart
@@ -9,8 +9,8 @@ import 'package:analyzer/src/generated/element.dart';
 import 'package:analyzer/src/generated/resolver.dart';
 
 import 'package:dev_compiler/src/info.dart';
-import 'package:dev_compiler/src/options.dart';
 import 'package:dev_compiler/src/utils.dart' as utils;
+import 'package:dev_compiler/strong_mode.dart' show StrongModeOptions;
 
 abstract class TypeRules {
   final TypeProvider provider;
@@ -116,7 +116,7 @@ typedef void MissingTypeReporter(Expression expr);
 
 class RestrictedRules extends TypeRules {
   MissingTypeReporter reportMissingType = null;
-  final RulesOptions options;
+  final StrongModeOptions options;
   final List<DartType> _nonnullableTypes;
   DownwardsInference inferrer;