load.js

javascript:(function(){
    var el = document.createElement('script');
    el.onload = el.onreadystatechange = function () {
        if (el.readyState && el.readyState !== "complete" && el.readyState !== "loaded") {
            return false;
        }
        btr.loadGist({ id: '1e363e357fe247b4db36b5e8fdd2243c', file: 'main.js' });
    };
    document.getElementsByTagName('head')[0].appendChild(el).src = 'https://cdn.rawgit.com/bastsoft/btr/v0.1.0/btr.js';
})();

main.js

var css = [
'::-webkit-scrollbar {',
'width: 19px;',
'}',
'::-webkit-scrollbar-track {',
'-webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.3); ',
'}',
'::-webkit-scrollbar-thumb {',
'background: #e2e2e2;',
'-webkit-box-shadow: inset 0 0 6px rgba(0,0,0,0.5);',
'}',
'::-webkit-scrollbar-thumb:window-inactive {',
'background: rgba(255,0,0,0.4);',
'}' 
].join("\n"),
    head = document.head || document.getElementsByTagName('head')[0],
    style = document.createElement('style');

style.type = 'text/css';
if (style.styleSheet){
  style.styleSheet.cssText = css;
} else {
  style.appendChild(document.createTextNode(css));
}

head.appendChild(style);

alert('done');