analyzer_exp fixes

pkg/analyzer_experimental/lib/src/error.dart

 // Copyright (c) 2013, 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.
 library error;
 
 import 'dart:collection';
-import 'dart:io';
 import 'dart:math' as math;
 
 import 'generated/error.dart';
 import 'generated/java_core.dart';
 import 'generated/source.dart';
 
 /// The maximum line length when printing extracted source code when converting
 /// an [AnalyzerError] to a string.
 final _MAX_ERROR_LINE_LENGTH = 120;
 
@@ skipping 78 matching lines @@
 class _ContentReceiver implements Source_ContentReceiver {
   final _buffer = new StringBuffer();
 
   String get result => _buffer.toString();
 
   void accept(CharBuffer contents, _) =>
     _buffer.write(contents.subSequence(0, contents.length()));
 
   void accept2(String contents, _) => _buffer.write(contents);
 }