Make zero-termination optional.

pkg/front_end/lib/src/fasta/scanner/io.dart

 // Copyright (c) 2016, 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.md file.
 
 library fasta.scanner.io;
 
 import 'dart:async' show Future;
 
 import 'dart:io' show File, RandomAccessFile;
 
 import 'dart:typed_data' show Uint8List;
 
 List<int> readBytesFromFileSync(Uri uri) {
   RandomAccessFile file = new File.fromUri(uri).openSync();
   Uint8List list;
   try {
     int length = file.lengthSync();
     // +1 to have a 0 terminated list, see [Scanner].
     list = new Uint8List(length + 1);
     file.readIntoSync(list, 0, length);
   } finally {
     file.closeSync();
   }
   return list;
 }
 
-Future<List<int>> readBytesFromFile(Uri uri) async {
+Future<List<int>> readBytesFromFile(Uri uri,
+    {bool ensureZeroTermination: true}) async {
   RandomAccessFile file = await new File.fromUri(uri).open();
   Uint8List list;
   try {
     int length = await file.length();
     // +1 to have a 0 terminated list, see [Scanner].
-    list = new Uint8List(length + 1);
+    list = new Uint8List(ensureZeroTermination ? length + 1 : length);
     int read = await file.readInto(list);
     if (read != length) {
       throw "Error reading file: ${uri}";
     }
   } finally {
     await file.close();
   }
   return list;
 }