Roll Observatory packages and add a roll script

path/lib/src/style/posix.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 path.style.posix;
-
-import '../characters.dart' as chars;
-import '../parsed_path.dart';
-import '../internal_style.dart';
-
-/// The style for POSIX paths.
-class PosixStyle extends InternalStyle {
-  PosixStyle();
-
-  final name = 'posix';
-  final separator = '/';
-  final separators = const ['/'];
-
-  // Deprecated properties.
-
-  final separatorPattern = new RegExp(r'/');
-  final needsSeparatorPattern = new RegExp(r'[^/]$');
-  final rootPattern = new RegExp(r'^/');
-  final relativeRootPattern = null;
-
-  bool containsSeparator(String path) => path.contains('/');
-
-  bool isSeparator(int codeUnit) => codeUnit == chars.SLASH;
-
-  bool needsSeparator(String path) =>
-      path.isNotEmpty && !isSeparator(path.codeUnitAt(path.length - 1));
-
-  int rootLength(String path) {
-    if (path.isNotEmpty && isSeparator(path.codeUnitAt(0))) return 1;
-    return 0;
-  }
-
-  bool isRootRelative(String path) => false;
-
-  String getRelativeRoot(String path) => null;
-
-  String pathFromUri(Uri uri) {
-    if (uri.scheme == '' || uri.scheme == 'file') {
-      return Uri.decodeComponent(uri.path);
-    }
-    throw new ArgumentError("Uri $uri must have scheme 'file:'.");
-  }
-
-  Uri absolutePathToUri(String path) {
-    var parsed = new ParsedPath.parse(path, this);
-    if (parsed.parts.isEmpty) {
-      // If the path is a bare root (e.g. "/"), [components] will
-      // currently be empty. We add two empty components so the URL constructor
-      // produces "file:///", with a trailing slash.
-      parsed.parts.addAll(["", ""]);
-    } else if (parsed.hasTrailingSeparator) {
-      // If the path has a trailing slash, add a single empty component so the
-      // URI has a trailing slash as well.
-      parsed.parts.add("");
-    }
-
-    return new Uri(scheme: 'file', pathSegments: parsed.parts);
-  }
-}