Add toUri and fromUri functions to pathos.

pkg/analyzer_experimental/lib/src/utils.dart

-// Copyright (c) 2013, 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 utils;
-
-import 'dart:io';
-
-import 'package:pathos/path.dart' as pathos;
-
-/// Converts a local path string to a `file:` [Uri].
-Uri pathToFileUri(String pathString) {
-  pathString = pathos.absolute(pathString);
-  if (Platform.operatingSystem != 'windows') {
-    return Uri.parse('file://$pathString');
-  } else if (pathos.rootPrefix(pathString).startsWith('\\\\')) {
-    // Network paths become "file://hostname/path/to/file".
-    return Uri.parse('file:${pathString.replaceAll("\\", "/")}');
-  } else {
-    // Drive-letter paths become "file:///C:/path/to/file".
-    return Uri.parse('file:///${pathString.replaceAll("\\", "/")}');
-  }
-}