Don't use mirrors in pkg/path.

pkg/path/lib/path.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.
 
 /// A comprehensive, cross-platform path manipulation library.
 ///
 /// ## Installing ##
 ///
 /// Use [pub][] to install this package. Add the following to your
 /// `pubspec.yaml` file.
@@ skipping 28 matching lines @@
 /// underlying platform that the program is running on, you can create a
 /// [Builder] and give it an explicit [Style]:
 ///
 ///     var builder = new path.Builder(style: Style.windows);
 ///     builder.join("directory", "file.txt");
 ///
 /// This will join "directory" and "file.txt" using the Windows path separator,
 /// even when the program is run on a POSIX machine.
 library path;
 
-@MirrorsUsed(targets: 'dart.dom.html.window, '
-    'dart.io.Directory.current, '
-    'dart.io.Platform.operatingSystem')
-import 'dart:mirrors';
-
 /// An internal builder for the current OS so we can provide a straight
 /// functional interface and not require users to create one.
 final _builder = new Builder();
 
 /// A default builder for manipulating POSIX paths.
 final posix = new Builder(style: Style.posix);
 
 /// A default builder for manipulating Windows paths.
 final windows = new Builder(style: Style.windows);
 
 /// A default builder for manipulating URLs.
 final url = new Builder(style: Style.url);
 
 /// Inserts [length] elements in front of the [list] and fills them with the
 /// [fillValue].
 void _growListFront(List list, int length, fillValue) =>
   list.insertAll(0, new List.filled(length, fillValue));
 
-/// If we're running in the server-side Dart VM, this will return a
-/// [LibraryMirror] that gives access to the `dart:io` library.
-///
-/// If `dart:io` is not available, this returns null.
-LibraryMirror get _io => currentMirrorSystem().libraries[Uri.parse('dart:io')];
-
-// TODO(nweiz): when issue 6490 or 6943 are fixed, make this work under dart2js.
-/// If we're running in Dartium, this will return a [LibraryMirror] that gives
-/// access to the `dart:html` library.
-///
-/// If `dart:html` is not available, this returns null.
-LibraryMirror get _html =>
-  currentMirrorSystem().libraries[Uri.parse('dart:html')];
 
 /// Gets the path to the current working directory.
 ///
 /// In the browser, this means the current URL. When using dart2js, this
 /// currently returns `.` due to technical constraints. In the future, it will
 /// return the current URL.
 String get current {
-  if (_io != null) {
-    return (_io.declarations[#Directory] as ClassMirror)
-        .getField(#current).reflectee.path;
-  } else if (_html != null) {
-    return _html.getField(#window).reflectee.location.href;
+  var uri = Uri.base;
+  if (Style.platform == Style.url) {
+    return uri.toString();
   } else {
-    return '.';
+    var path = uri.toFilePath();
+    // Remove trailing '/' or '\'.
+    return path.substring(0, path.length - 1);
   }
 }
 
 /// Gets the path separator for the current platform. This is `\` on Windows
 /// and `/` on other platforms (including the browser).
 String get separator => _builder.separator;
 
 /// Converts [path] to an absolute path by resolving it relative to the current
 /// working directory. If [path] is already an absolute path, just returns it.
 ///
@@ skipping 750 matching lines @@
   static final url = new _UrlStyle();
 
   /// The style of the host platform.
   ///
   /// When running on the command line, this will be [windows] or [posix] based
   /// on the host operating system. On a browser, this will be [url].
   static final platform = _getPlatformStyle();
 
   /// Gets the type of the host platform.
   static Style _getPlatformStyle() {
-    if (_io == null) return Style.url;
-
-    if ((_io.declarations[#Platform] as ClassMirror).getField(#operatingSystem)
-        .reflectee == 'windows') {
-      return Style.windows;
-    }
-
+    if (Uri.base.scheme != 'file') return Style.url;

[Bob Nystrom, 2013/11/06 18:00:36]

This does the wrong thing if you open a file in Dartium. You shouldn't get
Windows or POSIX path semantics within a browser just because you happened to
have opened a local file.

[Anders Johnsen, 2013/11/06 18:07:10]

Ahh, interesting point. I'll see if I can come up with a better way to detect
it.

+    if (new Uri.file('a/b').toFilePath() == 'a\\b') return Style.windows;
     return Style.posix;
   }
 
   /// The name of this path style. Will be "posix" or "windows".
   String get name;
 
   /// The path separator for this style. On POSIX, this is `/`. On Windows,
   /// it's `\`.
   String get separator;
 
@@ skipping 311 matching lines @@
     // doesn't count.
     if (lastDot <= 0) return [file, ''];
 
     return [file.substring(0, lastDot), file.substring(lastDot)];
   }
 
   _ParsedPath clone() => new _ParsedPath(
       style, root, isRootRelative,
       new List.from(parts), new List.from(separators));
 }