_getDefaultSwfPath = function() {
    var jsDir = _getDirPathOfUrl(_getCurrentScriptUrl()) || _getUnanimousScriptParentDir() || "";
    return jsDir + "ZeroClipboard.swf";
  }
Get the presumed location of the "ZeroClipboard.swf" file, based on the location
of the executing JavaScript file (e.g. "ZeroClipboard.js", etc.).

@returns String
@private