Update parser so tests pass.

pkg/dart_scanner/lib/dart_scanner.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 dart_scanner;
 
 import 'src/token.dart' show
     Token;
 
 import 'src/utf8_bytes_scanner.dart' show
@@ skipping 12 matching lines @@
 }
 
 ScannerResult scan(List<int> bytes, {bool includeComments: false}) {
   if (bytes.last != 0) {
     throw new ArgumentError("[bytes]: the last byte must be null.");
   }
   Scanner scanner =
       new Utf8BytesScanner(bytes, includeComments: includeComments);
   return new ScannerResult(scanner.tokenize(), scanner.lineStarts);
 }