Constructor.
string $pattern A regex for checking the asset's target URL:
FilterInterface $filter A filter to apply if the regex matches:
integer $flags Flags for what to check:
public function __construct($pattern, FilterInterface $filter, $flags = null) {
if (null === $flags) {
$flags = self::CHECK_SOURCE | self::CHECK_TARGET;
}
$this->pattern = $pattern;
$this->filter = $filter;
$this->flags = $flags;
}