POSIX: make sure that we never pass directory descriptors into the sandbox.

BUG=43304

http://codereview.chromium.org/2733011/show

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@49446 0039d316-1c4b-4281-b951-d872f2087c98
 void FileDescriptorSet::CommitAll() {
   for (std::vector<base::FileDescriptor>::iterator
        i = descriptors_.begin(); i != descriptors_.end(); ++i) {
    if (i->auto_close)
      HANDLE_EINTR(close(i->fd));
  }
  descriptors_.clear();
  consumed_descriptor_highwater_ = 0;
}

 void FileDescriptorSet::CommitAll() {
   for (std::vector<base::FileDescriptor>::iterator
        i = descriptors_.begin(); i != descriptors_.end(); ++i) {
    if (i->auto_close)
      HANDLE_EINTR(close(i->fd));
  }
  descriptors_.clear();
  consumed_descriptor_highwater_ = 0;
}
