fix issues caught by analysis_server

bin/edit_files.dart

 #!/usr/bin/env dart
 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /// Command line tool to write checker errors as inline comments in the source
 /// code of the program. This tool requires the info.json file created by
 /// running devc.dart passing the arguments
 /// --dump-info --dump-info-file info.json
 
 library dev_compiler.bin.edit_files;
 
 import 'dart:io';
 import 'dart:convert';
 
 import 'package:analyzer/src/generated/engine.dart' show AnalysisContext;
 import 'package:analyzer/src/generated/source.dart' show Source;
 import 'package:args/args.dart';
 import 'package:cli_util/cli_util.dart' show getSdkDir;
 import 'package:source_maps/refactor.dart';
 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")
   ..addOption('checkout-files-executable',
       help: 'Executable to check out files from source control (e.g. svn)',
       defaultsTo: null)
   ..addOption('checkout-files-arg',
       help: 'Arg to check out files from source control (e.g. checkout)',
       defaultsTo: null)
   ..addOption('include-pattern',
@@ skipping 115 matching lines @@
       : null;
 
   var context =
       createAnalysisContextWithSources(new StrongModeOptions(), options);
   var visitor = new EditFileSummaryVisitor(context, args['level'],
       args['checkout-files-executable'], args['checkout-files-arg'],
       includePattern, excludePattern);
   summary.accept(visitor);
   visitor.build();
 }