Remove the checker and corresponding dead code

bin/edit_files.dart

Index: bin/edit_files.dart
diff --git a/bin/edit_files.dart b/bin/edit_files.dart
index c7344df95e04bbf27fe4e71226bd4a1fdefc9359..e81c254ee1cdc5a6fd8e3f47c3b9462cb123c6e0 100644
--- a/bin/edit_files.dart
+++ b/bin/edit_files.dart
@@ -23,7 +23,6 @@ import 'package:source_span/source_span.dart';
 import 'package:dev_compiler/src/analysis_context.dart';
 import 'package:dev_compiler/src/options.dart';
 import 'package:dev_compiler/src/summary.dart';
-import 'package:dev_compiler/strong_mode.dart';
 
 final ArgParser argParser = new ArgParser()
   ..addOption('level', help: 'Minimum error level', defaultsTo: "info")
@@ -154,8 +153,7 @@ void main(List<String> argv) {
       ? new RegExp(args['include-pattern'])
       : null;
 
-  var context =
-      createAnalysisContextWithSources(new StrongModeOptions(), options);
+  var context = createAnalysisContextWithSources(options);
   var visitor = new EditFileSummaryVisitor(
       context,
       args['level'],