Don't include the trailing \0 of input bytes, in the string representation of source files.

pkg/compiler/lib/src/io/source_file.dart

 // Copyright (c) 2012, 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 dart2js.io.source_file;
 
 import 'dart:math';
 import 'dart:convert' show UTF8;
 
 import 'line_column_provider.dart';
@@ skipping 158 matching lines @@
 }
 
 class Utf8BytesSourceFile extends SourceFile {
   final Uri uri;
 
   /** The UTF-8 encoded content of the source file. */
   final List<int> content;
 
   Utf8BytesSourceFile(this.uri, this.content);
 
-  String slowText() => UTF8.decode(content);
+  String slowText() {
+    // Don't include the last '0' used by the scanner.
+    return UTF8.decode(content.sublist(0, content.length - 1));
+  }
 
   List<int> slowUtf8Bytes() => content;
 
   String slowSubstring(int start, int end) {
     // TODO(lry): to make this faster, the scanner could record the UTF-8 slack
     // for all positions of the source text. We could use [:content.sublist:].
     return slowText().substring(start, end);
   }
 
   int get length {
@@ skipping 37 matching lines @@
 
   int get length => text.length;
   set length(int v) { }
 
   String slowText() => text;
 
   List<int> slowUtf8Bytes() => UTF8.encode(text);
 
   String slowSubstring(int start, int end) => text.substring(start, end);
 }