Remove deprecated Strings class.

sdk/lib/io/path_impl.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.
 
 part of dart.io;
 
 class _Path implements Path {
   final String _path;
   final bool isWindowsShare;
 
@@ skipping 85 matching lines @@
     }
     for (int i = common; i < pathSegments.length; i++) {
       segments.add('${pathSegments[i]}');
     }
     if (segments.isEmpty) {
       segments.add('.');
     }
     if (hasTrailingSeparator) {
         segments.add('');
     }
-    return new Path(Strings.join(segments, '/'));
+    return new Path(segments.join('/'));
   }
 
 
   Path join(Path further) {
     if (further.isAbsolute) {
       throw new ArgumentError(
           "Path.join called with absolute Path as argument.");
     }
     if (isEmpty) {
       return further.canonicalize();
@@ skipping 86 matching lines @@
         segmentsToJoin.add('');
       } else {
         segmentsToJoin.add('.');
       }
     } else {
       segmentsToJoin.addAll(newSegs);
       if (hasTrailingSeparator) {
         segmentsToJoin.add('');
       }
     }
-    return new _Path._internal(Strings.join(segmentsToJoin, '/'),
-                               isWindowsShare);
+    return new _Path._internal(segmentsToJoin.join('/'), isWindowsShare);
   }
 
   String toNativePath() {
     if (Platform.operatingSystem == 'windows') {
       String nativePath = _path;
       // Drop '/' before a drive letter.
       if (nativePath.length >= 3 &&
           nativePath.startsWith('/') &&
           nativePath[2] == ':') {
         nativePath = nativePath.substring(1);
@@ skipping 43 matching lines @@
     while (pos > 0 && _path[pos - 1] == '/') --pos;
     var dirPath = (pos > 0) ? _path.substring(0, pos) : '/';
     return new _Path._internal(dirPath, isWindowsShare);
   }
 
   String get filename {
     int pos = _path.lastIndexOf('/');
     return _path.substring(pos + 1);
   }
 }