Fix directory test for windows

runtime/bin/directory_test.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.
 
 #include "bin/directory.h"
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/isolate.h"
 #include "vm/thread.h"
 #include "vm/unit_test.h"
 
 namespace dart {
 
 UNIT_TEST_CASE(DirectoryCurrentNoScope) {
   char* current_dir = dart::bin::Directory::CurrentNoScope();
   EXPECT_NOTNULL(current_dir);
   free(current_dir);
 }
 
 
-UNIT_TEST_CASE(DirectoryExists) {
-  char* current_dir = dart::bin::Directory::CurrentNoScope();
-  EXPECT_NOTNULL(current_dir);
-
-  dart::bin::Directory::ExistsResult r =
-      dart::bin::Directory::Exists(current_dir);
-  EXPECT_EQ(dart::bin::Directory::EXISTS, r);
-
-  free(current_dir);
-}
-
-
 TEST_CASE(DirectoryCurrent) {
   const char* current = dart::bin::Directory::Current();
   EXPECT_NOTNULL(current);
 }
 
 
+TEST_CASE(DirectoryExists) {
+  const char* current = dart::bin::Directory::Current();
+  EXPECT_NOTNULL(current);
+
+  dart::bin::Directory::ExistsResult r =
+      dart::bin::Directory::Exists(current);
+  EXPECT_EQ(dart::bin::Directory::EXISTS, r);
+}
+
+
 TEST_CASE(DirectorySystemTemp) {
   const char* system_temp = dart::bin::Directory::SystemTemp();
   EXPECT_NOTNULL(system_temp);
 }
 
 
 TEST_CASE(DirectoryCreateTemp) {
   const char* kTempPrefix = "test_prefix";
   const char* system_temp = dart::bin::Directory::SystemTemp();
   EXPECT_NOTNULL(system_temp);
@@ skipping 85 matching lines @@
 
   r = dart::bin::Directory::Exists(name);
   EXPECT_EQ(dart::bin::Directory::DOES_NOT_EXIST, r);
 
   EXPECT(dart::bin::Directory::Delete(new_name, false));
   delete[] name;
   delete[] new_name;
 }
 
 }  // namespace dart