dart2js: Handle zero-terminated content explicitly.

tests/compiler/dart2js/scanner_test.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.
 
 import "package:expect/expect.dart";
 import 'package:compiler/src/scanner/scannerlib.dart';
 import 'package:compiler/src/util/characters.dart';
 import 'dart:typed_data';
 
-Token scan(List<int> bytes) => new Utf8BytesScanner.fromBytes(bytes).tokenize();
+Token scan(List<int> bytes) {
+  List<int> zeroTerminated = new Uint8List(bytes.length + 1);
+  zeroTerminated.setRange(0, bytes.length, bytes);
+  zeroTerminated[bytes.length] = 0;
+  return new Utf8BytesScanner.fromBytes(zeroTerminated).tokenize();
+}
 
 Token scanUTF8(List<int> bytes) {
   int l = bytes.length;
   List<int> stringLiteral = new Uint8List(l + 3);
   stringLiteral[0] = 0x27; // single quote
   stringLiteral[l+1] = 0x27; // single quote
+  // The bytes given to the scanner must be 0-terminated.
   stringLiteral[l+2] = $EOF;
   for (int i = 0; i < l; i++) {
     stringLiteral[i+1] = bytes[i];
   }
   return new Utf8BytesScanner.fromBytes(stringLiteral).tokenize();
 }
 
 bool isRunningOnJavaScript() => identical(1, 1.0);
 
 main() {
@@ skipping 37 matching lines @@
   // "#!"
   token = scan([0x23, 0x21]);
   Expect.equals(token.info, EOF_INFO); // Treated as a comment.
 
   // Regression test for issue 1761.
   // "#! Hello, World!"
   token = scan([0x23, 0x21, 0x20, 0x48, 0x65, 0x6c, 0x6c, 0x6f, 0x2c, 0x20,
                 0x57, 0x6f, 0x72, 0x6c, 0x64, 0x21]);
   Expect.equals(token.info, EOF_INFO); // Treated as a comment.
 }