Fix directory-listing to return a future on cancel.

runtime/bin/directory_win.cc

Index: runtime/bin/directory_win.cc
diff --git a/runtime/bin/directory_win.cc b/runtime/bin/directory_win.cc
index e3e390f4292ac0bd7328ced0f9a65869afe5a457..3733a71384e5d734f7d4b52d1694aba85875238f 100644
--- a/runtime/bin/directory_win.cc
+++ b/runtime/bin/directory_win.cc
@@ -206,14 +206,18 @@ ListType DirectoryListingEntry::Next(DirectoryListing* listing) {
     return kListError;
   }
 
-  if (FindClose(reinterpret_cast<HANDLE>(lister_)) == 0) {
-    return kListError;
-  }
-
   return kListDone;
 }
 
 
+DirectoryListingEntry::~DirectoryListingEntry() {
+  ResetLink();
+  if (lister_ != 0) {
+    FindClose(reinterpret_cast<HANDLE>(lister_));
+  }
+}
+
+
 void DirectoryListingEntry::ResetLink() {
   if (link_ != NULL && (parent_ == NULL || parent_->link_ != link_)) {
     delete link_;