Add uri getter on file system entity.

sdk/lib/io/file.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.
 
 part of dart.io;
 
 /**
  * The modes in which a File can be opened.
  */
 class FileMode {
@@ skipping 80 matching lines @@
  * A more flexible and useful way to read a file is with a [Stream].
  * Open the file with [openRead], which returns a stream that
  * provides the data in the file as chunks of bytes.
  * Listen to the stream for data and process as needed.
  * You can use various transformers in succession to manipulate the
  * data into the required format or to prepare it for output.
  *
  * You might want to use a stream to read large files,
  * to manipulate the data with tranformers,
  * or for compatibility with another API, such as [WebSocket]s.
- * 
+ *
  *     import 'dart:io';
  *     import 'dart:convert';
  *     import 'dart:async';
  *
  *     main() {
  *       final file = new File('file.txt');
  *       Stream<List<int>> inputStream = file.openRead();
  *
  *       inputStream
  *         .transform(UTF8.decoder)       // Decode bytes to UTF8.
@@ skipping 17 matching lines @@
  *         .then((File file) {
  *           // Do something with the file.
  *         });
  *     }
  *
  * You can also write to a file using a [Stream]. Open the file with
  * [openWrite], which returns a stream to which you can write data.
  * Be sure to close the file with the [close] method.
  *
  *     import 'dart:io';
- *    
+ *
  *     void main() {
  *       var file = new File('file.txt');
  *       var sink = file.openWrite();
  *       sink.write('FILE ACCESSED ${new DateTime.now()}\n');
  *
  *       // Close the IOSink to free system resources.
  *       sink.close();
  *     }
  *
  * ## The use of Futures
  *
  * To avoid unintentional blocking of the program,
  * several methods use a [Future] to return a value. For example,
  * the [length] method, which gets the length of a file, returns a Future.
  * Use `then` to register a callback function, which is called when
  * the value is ready.
  *
  *     import 'dart:io';
  *
  *     main() {
  *       final file = new File('file.txt');
- *     
+ *
  *       file.length().then((len) {
  *         print(len);
  *       });
  *     }
  *
  * In addition to length, the [exists], [lastModified], [stat], and
  * other methods, return Futures.
  *
  * ## Other resources
  *
  * * [Dart by Example](https://www.dartlang.org/dart-by-example/#files-directories-and-symlinks)
- * provides additional task-oriented code samples that show how to use 
+ * provides additional task-oriented code samples that show how to use
  * various API from the Directory class and the related [File] class.
  *
  * * [I/O for Command-Line Apps](https://www.dartlang.org/docs/dart-up-and-running/contents/ch03.html#ch03-dartio---file-and-socket-io-for-command-line-apps)
  * a section from _A Tour of the Dart Libraries_
  * covers files and directories.
  *
  * * [Write Command-Line Apps](https://www.dartlang.org/docs/tutorials/cmdline/),
  * a tutorial about writing command-line apps, includes information
  * about files and directories.
 
  */
-abstract class File extends FileSystemEntity {
+abstract class File implements FileSystemEntity {
   /**
    * Creates a [File] object.
    *
    * If [path] is a relative path, it will be interpreted relative to the
    * current working directory (see [Directory.current]), when used.
    *
    * If [path] is an absolute path, it will be immune to changes to the
    * current working directory.
    */
   factory File(String path) => new _File(path);
@@ skipping 665 matching lines @@
       sb.write(": $osError");
       if (path != null) {
         sb.write(", path = '$path'");
       }
     } else if (path != null) {
       sb.write(": $path");
     }
     return sb.toString();
   }
 }