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

runtime/bin/file.h

Index: runtime/bin/file.h
diff --git a/runtime/bin/file.h b/runtime/bin/file.h
index deffe0e42c4d2ed5cf28fd173d0ae1cc6affee35..16ff0fcac15b316f7d280263f365bd13b72836ae 100644
--- a/runtime/bin/file.h
+++ b/runtime/bin/file.h
@@ -88,6 +88,7 @@ class File {
   static bool Delete(const char* name);
   static bool IsAbsolutePath(const char* pathname);
   static char* GetCanonicalPath(const char* name);
+  static char* GetContainingDirectory(char* name);
   static const char* PathSeparator();
   static const char* StringEscapedPathSeparator();
   static StdioHandleType GetStdioHandleType(int fd);