Split dart:builtin into dart:builtin and dart:io.

frog/leg/scanner/vm_scanner_bench.dart

-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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('vm_scanner_bench');
+#import('dart:io');
 #import('scannerlib.dart');
 #import('scanner_implementation.dart');
 #import('scanner_bench.dart');
 #import('../../../utils/utf8/utf8.dart');
 #import('../util/characters.dart');
 #source('byte_strings.dart');
 #source('byte_array_scanner.dart');
 
 class VmScannerBench extends ScannerBench {
   int getBytes(String filename, void callback(List<int> bytes)) {
@@ skipping 13 matching lines @@
       print("no such file: ${filename}");
     }
   }
 
   Scanner makeScanner(bytes) => new ByteArrayScanner(bytes);
 }
 
 main() {
   new VmScannerBench().main(argv);
 }