Fix directory-listing to return a future on cancel.

runtime/bin/directory.h

 // 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.
 
 #ifndef BIN_DIRECTORY_H_
 #define BIN_DIRECTORY_H_
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 #include "platform/globals.h"
@@ skipping 47 matching lines @@
 // later on.
 //
 // The stack is managed by the DirectoryListing's PathBuffer. Each
 // DirectoryListingEntry stored a entry-length, that it'll reset the PathBuffer
 // to on each call to Next.
 class DirectoryListingEntry {
  public:
   explicit DirectoryListingEntry(DirectoryListingEntry* parent)
     : parent_(parent), lister_(0), done_(false), link_(NULL) {}
 
-  ~DirectoryListingEntry() {
-    ResetLink();
-  }
+  ~DirectoryListingEntry();
 
   ListType Next(DirectoryListing* listing);
 
   DirectoryListingEntry* parent() const {
     return parent_;
   }
 
   LinkList* link() {
     return link_;
   }
@@ skipping 193 matching lines @@
 
  private:
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(Directory);
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // BIN_DIRECTORY_H_