Fixes leak of native File objects.

runtime/bin/file_patch.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.
 
 patch class _File {
   /* patch */ static _exists(String path) native "File_Exists";
   /* patch */ static _create(String path) native "File_Create";
   /* patch */ static _createLink(String path, String target)
       native "File_CreateLink";
   /* patch */ static _linkTarget(String path) native "File_LinkTarget";
   /* patch */ static _deleteNative(String path) native "File_Delete";
   /* patch */ static _deleteLinkNative(String path) native "File_DeleteLink";
   /* patch */ static _rename(String oldPath, String newPath)
       native "File_Rename";
   /* patch */ static _renameLink(String oldPath, String newPath)
       native "File_RenameLink";
   /* patch */ static _copy(String oldPath, String newPath) native "File_Copy";
   /* patch */ static _lengthFromPath(String path) native "File_LengthFromPath";
   /* patch */ static _lastModified(String path) native "File_LastModified";
   /* patch */ static _open(String path, int mode) native "File_Open";
   /* patch */ static int _openStdio(int fd) native "File_OpenStdio";
 }
 
 
-patch class _RandomAccessFile {
-  /* patch */ static int _close(int id) native "File_Close";
-  /* patch */ static int _getFD(int id) native "File_GetFD";
-  /* patch */ static _readByte(int id) native "File_ReadByte";
-  /* patch */ static _read(int id, int bytes) native "File_Read";
-  /* patch */ static _readInto(int id, List<int> buffer, int start, int end)
-      native "File_ReadInto";
-  /* patch */ static _writeByte(int id, int value) native "File_WriteByte";
-  /* patch */ static _writeFrom(int id, List<int> buffer, int start, int end)
-      native "File_WriteFrom";
-  /* patch */ static _position(int id) native "File_Position";
-  /* patch */ static _setPosition(int id, int position)
-      native "File_SetPosition";
-  /* patch */ static _truncate(int id, int length) native "File_Truncate";
-  /* patch */ static _length(int id) native "File_Length";
-  /* patch */ static _flush(int id) native "File_Flush";
-  /* patch */ static _lock(int id, int lock, int start, int end)
-      native "File_Lock";
+patch class _RandomAccessFileOps {
+  /* patch */ factory _RandomAccessFileOps(int pointer)
+      => new _RandomAccessFileOpsImpl(pointer);
 }
 
 
+class _RandomAccessFileOpsImpl extends NativeFieldWrapperClass1
+                               implements _RandomAccessFileOps {
+  _RandomAccessFileOpsImpl._();
+
+  factory _RandomAccessFileOpsImpl(int pointer)
+      => new _RandomAccessFileOpsImpl._().._setPointer(pointer);
+
+  void _setPointer(int pointer) native "File_SetPointer";
+
+  int getPointer() native "File_GetPointer";
+  int close() native "File_Close";
+  readByte() native "File_ReadByte";
+  read(int bytes) native "File_Read";
+  readInto(List<int> buffer, int start, int end) native "File_ReadInto";
+  writeByte(int value) native "File_WriteByte";
+  writeFrom(List<int> buffer, int start, int end) native "File_WriteFrom";
+  position() native "File_Position";
+  setPosition(int position) native "File_SetPosition";
+  truncate(int length) native "File_Truncate";
+  length() native "File_Length";
+  flush() native "File_Flush";
+  lock(int lock, int start, int end) native "File_Lock";
+}
+
+
 class _WatcherPath {
   final int pathId;
   final String path;
   final int events;
   int count = 0;
   _WatcherPath(this.pathId, this.path, this.events);
 }
 
 
 patch class _FileSystemWatcher {
@@ skipping 309 matching lines @@
   void _pathWatchedEnd() {
     _subscription.cancel();
     _controller.close();
   }
 }
 
 
 Uint8List _makeUint8ListView(Uint8List source, int offsetInBytes, int length) {
   return new Uint8List.view(source.buffer, offsetInBytes, length);
 }