Implement File.directory() and File.directorySync() to get

runtime/bin/file_win.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/file.h"
 
 #include <fcntl.h>
 #include <io.h>
 #include <stdio.h>
 #include <string.h>
@@ skipping 157 matching lines @@
 
 char* File::GetCanonicalPath(const char* pathname) {
   int required_size = GetFullPathName(pathname, 0, NULL, NULL);
   char* path = static_cast<char*>(malloc(required_size));
   int written = GetFullPathName(pathname, required_size, path, NULL);
   ASSERT(written == (required_size - 1));
   return path;
 }
 
 
+char* File::GetContainingDirectory(char* pathname) {
+  ASSERT(Exists(pathname));
+  int required_size = GetFullPathName(pathname, 0, NULL, NULL);
+  char* path = static_cast<char*>(malloc(required_size));
+  char* file_part = NULL;
+  int written = GetFullPathName(pathname, required_size, path, &file_part);
+  ASSERT(written == (required_size - 1));
+  ASSERT(file_part != NULL);
+  ASSERT(file_part > path);
+  ASSERT(file_part[-1] == '\\');
+  file_part[-1] = '\0';
+  return path;
+}
+
+
 const char* File::PathSeparator() {
   return "\\";
 }
 
 
 const char* File::StringEscapedPathSeparator() {
   return "\\\\";
 }
 
 
 File::StdioHandleType File::GetStdioHandleType(int fd) {
   // Treat all stdio handles as pipes. The Windows event handler and
   // socket code will handle the different handle types.
   return kPipe;
 }