Update charted to 0.4.8 and roll

packages/path/lib/src/utils.dart

 // Copyright (c) 2014, 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 path.utils;
-
 import 'characters.dart' as chars;
 
 /// Returns whether [char] is the code for an ASCII letter (uppercase or
 /// lowercase).
 bool isAlphabetic(int char) =>
     (char >= chars.UPPER_A && char <= chars.UPPER_Z) ||
         (char >= chars.LOWER_A && char <= chars.LOWER_Z);
 
 /// Returns whether [char] is the code for an ASCII digit.
 bool isNumeric(int char) => char >= chars.ZERO && char <= chars.NINE;
+
+/// Returns whether [path] has a URL-formatted Windows drive letter beginning at
+/// [index].
+bool isDriveLetter(String path, int index) {
+  if (path.length < index + 2) return false;
+  if (!isAlphabetic(path.codeUnitAt(index))) return false;
+  if (path.codeUnitAt(index + 1) != chars.COLON) return false;
+  if (path.length == index + 2) return true;
+  return path.codeUnitAt(index + 2) == chars.SLASH;
+}