Fix directory-listing to return a future on cancel.

runtime/bin/directory.cc

 // 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.
 
 #include "bin/directory.h"
 
 #include "bin/dartutils.h"
 #include "bin/thread.h"
 #include "include/dart_api.h"
 #include "platform/assert.h"
@@ skipping 244 matching lines @@
   return CreateIllegalArgumentError();
 }
 
 
 CObject* Directory::ListNextRequest(const CObjectArray& request) {
   if (request.Length() == 1 &&
       request[0]->IsIntptr()) {
     CObjectIntptr ptr(request[0]);
     AsyncDirectoryListing* dir_listing =
         reinterpret_cast<AsyncDirectoryListing*>(ptr.Value());
+    if (dir_listing->IsEmpty()) {
+      return new CObjectArray(CObject::NewArray(0));
+    }
     const int kArraySize = 128;
     CObjectArray* response = new CObjectArray(CObject::NewArray(kArraySize));
     dir_listing->SetArray(response, kArraySize);
     Directory::List(dir_listing);
     // In case the listing ended before it hit the buffer length, we need to
     // override the array length.
     response->AsApiCObject()->value.as_array.length = dir_listing->index();
     return response;
   }
   return CreateIllegalArgumentError();
@@ skipping 143 matching lines @@
   if (listing->error()) {
     listing->HandleError("Invalid path");
     listing->HandleDone();
   } else {
     while (ListNext(listing)) {}
   }
 }
 
 }  // namespace bin
 }  // namespace dart