Move delete/deleteSync up to FileSystemEntity, with a shared documentation.

sdk/lib/io/file_impl.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;
 
 // Read the file in blocks of size 64k.
 const int _BLOCK_SIZE = 64 * 1024;
 
 
@@ skipping 277 matching lines @@
 
   external static _createLink(String path, String target);
 
   external static _linkTarget(String path);
 
   void createSync() {
     var result = _create(path);
     throwIfError(result, "Cannot create file", path);
   }
 
-  Future<File> delete() {
+  Future<File> _delete({bool recursive: false}) {
+    if (recursive) {
+      return new Directory(path).delete(recursive: true).then((_) => this);
+    }
     _ensureFileService();
     List request = new List(2);
     request[0] = _DELETE_REQUEST;
     request[1] = path;
     return _fileService.call(request).then((response) {
       if (_isErrorResponse(response)) {
         throw _exceptionFromResponse(response, "Cannot delete file", path);
       }
       return this;
     });
   }
 
-  external static _delete(String path);
+  external static _deleteNative(String path);
 
-  external static _deleteLink(String path);
+  external static _deleteLinkNative(String path);
 
-  void deleteSync() {
-    var result = _delete(path);
+  void _deleteSync({bool recursive: false}) {
+    if (recursive) {
+      return new Directory(path).deleteSync(recursive: true);
+    }
+    var result = _deleteNative(path);
     throwIfError(result, "Cannot delete file", path);
   }
 
   Future<File> rename(String newPath) {
     _ensureFileService();
     List request = new List(3);
     request[0] = _RENAME_REQUEST;
     request[1] = path;
     request[2] = newPath;
     return _fileService.call(request).then((response) {
@@ skipping 650 matching lines @@
   void _checkNotClosed() {
     if (closed) {
       throw new FileException("File closed", path);
     }
   }
 
   Future _closedException() {
     return new Future.error(new FileException("File closed", path));
   }
 }