Allow Directory.create to create all missing path components.

sdk/lib/io/path_impl.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.
 
 class _Path implements Path {
   final String _path;
 
   _Path(String source) : _path = source;
   _Path.fromNative(String source) : _path = _clean(source);
 
@@ skipping 171 matching lines @@
         segmentsToJoin.add('');
       }
     }
     return new Path(Strings.join(segmentsToJoin, '/'));
   }
 
   String toNativePath() {
     if (Platform.operatingSystem == 'windows') {
       String nativePath = _path;
       // Drop '/' before a drive letter.
-      if (nativePath.length > 3 &&
+      if (nativePath.length >= 3 &&
           nativePath.startsWith('/') &&

[Søren Gjesse, 2012/11/06 10:45:26]

Now that you are at it maybe check that nativePath[1] is [A-Za-z].

[Mads Ager (google), 2012/11/06 15:00:35]

Not sure we have to. If you use this and it doesn't exist you will get an error
from the system anyway.

           nativePath[2] == ':') {
         nativePath = nativePath.substring(1);
       }
       nativePath = nativePath.replaceAll('/', '\\');
       return nativePath;
     }
     return _path;
   }
 
   List<String> segments() {
@@ skipping 31 matching lines @@
     if (pos < 0) return new Path('');
     while (pos > 0 && _path[pos - 1] == '/') --pos;
     return new Path((pos > 0) ? _path.substring(0, pos) : '/');
   }
 
   String get filename {
     int pos = _path.lastIndexOf('/');
     return _path.substring(pos + 1);
   }
 }