_extractDomain = function(originOrUrl) {
    if (originOrUrl == null || originOrUrl === "") {
      return null;
    }
    originOrUrl = originOrUrl.replace(/^\s+|\s+$/g, "");
    if (originOrUrl === "") {
      return null;
    }
    var protocolIndex = originOrUrl.indexOf("//");
    originOrUrl = protocolIndex === -1 ? originOrUrl : originOrUrl.slice(protocolIndex + 2);
    var pathIndex = originOrUrl.indexOf("/");
    originOrUrl = pathIndex === -1 ? originOrUrl : protocolIndex === -1 || pathIndex === 0 ? null : originOrUrl.slice(0, pathIndex);
    if (originOrUrl && originOrUrl.slice(-4).toLowerCase() === ".swf") {
      return null;
    }
    return originOrUrl || null;
  }
Extract the domain (e.g. "github.com") from an origin (e.g. "https://github.com") or
URL (e.g. "https://github.com/zeroclipboard/zeroclipboard/").

@returns the domain
@private