Serves a pre-gzipped static asset from the zip file.

def _serve_asset(self, path, gzipped_asset_bytes, request):
    """Serves a pre-gzipped static asset from the zip file."""
    mimetype = mimetypes.guess_type(path)[0] or 'application/octet-stream'
    return http_util.Respond(
        request, gzipped_asset_bytes, mimetype, content_encoding='gzip')