Update all occurrences of raw strings.

tests/standalone/io/path_test.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.
 //
 // Test the Path class in dart:io.
 
 #import("dart:io");
 
 void main() {
   testBaseFunctions();
@@ skipping 56 matching lines @@
                 'absolute canonical');
     testGetters(new Path.fromNative(r"foo/bar\hest/.fisk"),
                 ['foo/bar/hest', '.fisk', '', 'fisk'],
                 'canonical');
     testGetters(new Path.fromNative(r"foo//bar\\hest/\/.fisk."),
                 ['foo//bar//hest', '.fisk.', '.fisk', ''],
                 '');
   } else {
     // Make sure that backslashes are uninterpreted on other platforms.
     testGetters(new Path.fromNative(r"/foo\bar/bif/fisk.hest"),
-                [@'/foo\bar/bif', 'fisk.hest', 'fisk', 'hest'],
+                [r'/foo\bar/bif', 'fisk.hest', 'fisk', 'hest'],
                 'absolute canonical');
     testGetters(new Path.fromNative(r"//foo\bar///bif////fisk.hest"),
-                [@'//foo\bar///bif', 'fisk.hest', 'fisk', 'hest'],
+                [r'//foo\bar///bif', 'fisk.hest', 'fisk', 'hest'],
                 'absolute');
     testGetters(new Path.fromNative(r"/foo\ bar/bif/gule\ fisk.hest"),
-                [@'/foo\ bar/bif', @'gule\ fisk.hest', @'gule\ fisk', 'hest'],
+                [r'/foo\ bar/bif', r'gule\ fisk.hest', r'gule\ fisk', 'hest'],
                 'absolute canonical');
   }
 }
 
 
 void testGetters(Path path, List components, String properties) {
   final int DIRNAME = 0;
   final int FILENAME = 1;
   final int FILENAME_NO_EXTENSION = 2;
   final int EXTENSION = 3;
@@ skipping 78 matching lines @@
   Expect.equals('.',
                 new Path('/a').relativeTo(new Path('/a')).toString());
 
   // Not implemented yet.  Should return new Path('../b/c/d/').
   Expect.throws(() =>
                 new Path('b/c/d/').relativeTo(new Path('a/')));
   // Should always throw - no relative path can be constructed.
   Expect.throws(() =>
                 new Path('a/b').relativeTo(new Path('../../d')));
 }