Fix error handling when current working directory is deleted.

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"
 
 
 namespace dart {
 namespace bin {
 
 // Forward declaration.
 static void DirectoryService(Dart_Port, Dart_Port, Dart_CObject*);
 
 NativeService Directory::directory_service_("DirectoryService",
                                             DirectoryService,
                                             16);
 
 
 void FUNCTION_NAME(Directory_Current)(Dart_NativeArguments args) {
   char* current = Directory::Current();
   if (current != NULL) {
     Dart_SetReturnValue(args, DartUtils::NewString(current));
     free(current);
+  } else {
+    Dart_Handle err = DartUtils::NewDartOSError();
+    if (Dart_IsError(err)) Dart_PropagateError(err);
+    Dart_SetReturnValue(args, err);
   }
 }
 
 
 void FUNCTION_NAME(Directory_SetCurrent)(Dart_NativeArguments args) {
   int argc = Dart_GetNativeArgumentCount(args);
   Dart_Handle path;
   if (argc == 1) {
     path = Dart_GetNativeArgument(args, 0);
   }
@@ skipping 428 matching lines @@
   if (listing->error()) {
     listing->HandleError("Invalid path");
     listing->HandleDone();
   } else {
     while (ListNext(listing)) {}
   }
 }
 
 }  // namespace bin
 }  // namespace dart