Creates a directory within another directory. Extra characters will be
appended to |prefix| to ensure that the new directory does not have the same
name as an existing directory. Returns true (1) on success and sets
|new_dir| to the full path of the directory that was created. The directory
is only readable by the current user. Calling this function on the browser
process UI or IO threads is not allowed.
Creates a directory within another directory. Extra characters will be appended to |prefix| to ensure that the new directory does not have the same name as an existing directory. Returns true (1) on success and sets |new_dir| to the full path of the directory that was created. The directory is only readable by the current user. Calling this function on the browser process UI or IO threads is not allowed.