For running a optional javascript on the javascript console of Google Chrome.

default_optional_mine.js

alert('Hey! I am test alert!');

RunningOptionalJavascriptSnippets.txt

// This is a sample. jQuery will work fine on your console. 
(script = document.createElement('script')).src = 'http://code.jquery.com/jquery-latest.min.js';
document.getElementsByTagName('head')[0].appendChild(script);

// Optional javascript works on your console too. 
// Please modify next line to fit your infomation.
var username="jmatsu"; var gist_id="e5800eda726722decbda"; var filename="default_optional_mine.js";
(script2 = document.createElement('script')).src = 'https://rawgithub.com/'+username+'/'+gist_id+'/raw/'+filename;
document.getElementsByTagName('head')[0].appendChild(script2);

// Please remove caches and reload your browser if no change reflect.
// gist.github.com cannot run js file which is via gist because it violates the following Content Security Policy directive.