Fixes leak of native File objects.

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 733 matching lines @@
    * the process. Note that this does not actually lock the file for
    * access. Also note that advisory locks are on a process
    * level. This means that several isolates in the same process can
    * obtain an exclusive lock on the same file.
    *
    * On Windows the regions used for lock and unlock needs to match. If that
    * is not the case unlocking will result in the OS error "The segment is
    * already unlocked".
    */
   Future<RandomAccessFile> lock(
-      [FileLock mode = FileLock.EXCLUSIVE, int start = 0, int end]);
+      [FileLock mode = FileLock.EXCLUSIVE, int start = 0, int end = -1]);
 
   /**
    * Synchronously locks the file or part of the file.
    *
    * By default an exclusive lock will be obtained, but that can be overridden
    * by the [mode] argument.
    *
    * Locks the byte range from [start] to [end] of the file ,with the
    * byte at position `end` not included. If no arguments are
    * specified, the full file is locked, If only `start` is specified
@@ skipping 12 matching lines @@
    * the process. Note that this does not actually lock the file for
    * access. Also note that advisory locks are on a process
    * level. This means that several isolates in the same process can
    * obtain an exclusive lock on the same file.
    *
    * On Windows the regions used for lock and unlock needs to match. If that
    * is not the case unlocking will result in the OS error "The segment is
    * already unlocked".
    *
    */
-  void lockSync([FileLock mode = FileLock.EXCLUSIVE, int start = 0, int end]);
+  void lockSync(
+      [FileLock mode = FileLock.EXCLUSIVE, int start = 0, int end = -1]);
 
   /**
    * Unlocks the file or part of the file.
    *
    * Unlocks the byte range from [start] to [end] of the file, with
    * the byte at position `end` not included. If no arguments are
    * specified, the full file is unlocked, If only `start` is
    * specified the file is unlocked from byte position `start` to the
    * end of the file.
    *
    * *NOTE* file locking does have slight differences in behavior across
    * platforms:
    *
    * See [lock] for more details.
    */
-  Future<RandomAccessFile> unlock([int start = 0, int end]);
+  Future<RandomAccessFile> unlock([int start = 0, int end = -1]);
 
   /**
    * Synchronously unlocks the file or part of the file.
    *
    * Unlocks the byte range from [start] to [end] of the file, with
    * the byte at position `end` not included. If no arguments are
    * specified, the full file is unlocked, If only `start` is
    * specified the file is unlocked from byte position `start` to the
    * end of the file.
    *
    * *NOTE* file locking does have slight differences in behavior across
    * platforms:
    *
    * See [lockSync] for more details.
    */
-  void unlockSync([int start = 0, int end]);
+  void unlockSync([int start = 0, int end = -1]);
 
   /**
    * Returns a human-readable string for this RandomAccessFile instance.
    */
   String toString();
 
   /**
    * Gets the path of the file underlying this RandomAccessFile.
    */
   String get path;
@@ skipping 45 matching lines @@
       sb.write(": $osError");
       if (path != null) {
         sb.write(", path = '$path'");
       }
     } else if (path != null) {
       sb.write(": $path");
     }
     return sb.toString();
   }
 }