Really remove io support when dart:io is unsupported.

runtime/bin/directory_unsupported.cc

+// Copyright (c) 2016, 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.
+
+#if defined(DART_IO_DISABLED)
+
+#include "bin/builtin.h"
+#include "bin/dartutils.h"
+#include "include/dart_api.h"
+
+namespace dart {
+namespace bin {
+
+void FUNCTION_NAME(Directory_Current)(Dart_NativeArguments args) {
+  Dart_ThrowException(DartUtils::NewInternalError(
+        "Directory is not supported on this platform"));
+}
+
+
+void FUNCTION_NAME(Directory_SetCurrent)(Dart_NativeArguments args) {
+  Dart_ThrowException(DartUtils::NewInternalError(
+        "Directory is not supported on this platform"));
+}
+
+
+void FUNCTION_NAME(Directory_Exists)(Dart_NativeArguments args) {
+  Dart_ThrowException(DartUtils::NewInternalError(
+        "Directory is not supported on this platform"));
+}
+
+
+void FUNCTION_NAME(Directory_Create)(Dart_NativeArguments args) {
+  Dart_ThrowException(DartUtils::NewInternalError(
+        "Directory is not supported on this platform"));
+}
+
+
+void FUNCTION_NAME(Directory_SystemTemp)(Dart_NativeArguments args) {
+  Dart_ThrowException(DartUtils::NewInternalError(
+        "Directory is not supported on this platform"));
+}
+
+
+void FUNCTION_NAME(Directory_CreateTemp)(Dart_NativeArguments args) {
+  Dart_ThrowException(DartUtils::NewInternalError(
+        "Directory is not supported on this platform"));
+}
+
+
+void FUNCTION_NAME(Directory_Delete)(Dart_NativeArguments args) {
+  Dart_ThrowException(DartUtils::NewInternalError(
+        "Directory is not supported on this platform"));
+}
+
+
+void FUNCTION_NAME(Directory_Rename)(Dart_NativeArguments args) {
+  Dart_ThrowException(DartUtils::NewInternalError(
+        "Directory is not supported on this platform"));
+}
+
+
+void FUNCTION_NAME(Directory_List)(Dart_NativeArguments args) {
+  Dart_ThrowException(DartUtils::NewInternalError(
+        "Directory is not supported on this platform"));
+}
+
+}  // namespace bin
+}  // namespace dart
+
+#endif  // defined(DART_IO_DISABLED)