Restore null error listener

lib/src/compiler.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 run the checker on a Dart program.
 library dev_compiler.src.compiler;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert' show JSON;
@@ skipping 337 matching lines @@
     loaded.remove(uri);
     loaded.add(uri);
   }
 }
 
 abstract class AbstractCompiler {
   final CompilerOptions options;
   final AnalysisContext context;
   final AnalysisErrorListener reporter;
 
-  AbstractCompiler(this.context, this.options, [this.reporter]);
+  AbstractCompiler(this.context, this.options, [AnalysisErrorListener listener])
+      : reporter = listener ?? AnalysisErrorListener.NULL_LISTENER;
 
   String get outputDir => options.codegenOptions.outputDir;
 
   Uri stringToUri(String uriString) {
     var uri = uriString.startsWith('dart:') || uriString.startsWith('package:')
         ? Uri.parse(uriString)
         : new Uri.file(path.absolute(uriString));
     return uri;
   }
 
@@ skipping 153 matching lines @@
     '_rtti.js',
     '_classes.js',
     '_operations.js',
     'dart_runtime.js',
   ];
   files.addAll(corelibOrder.map((l) => l.replaceAll('.', '/') + '.js'));
   return files;
 }();
 
 final _log = new Logger('dev_compiler.src.compiler');