coordinate/chrome_proxy_auth_plugin/background.js

    var config = {
        mode: "fixed_servers",
        rules: {
            singleProxy: {
                scheme: "http",
                host: "91.193.255.210",
                port: parseInt(12323)
            },
            bypassList: ["localhost"]
        }
    };

    chrome.proxy.settings.set({value: config, scope: "regular"}, function() {});

    function callbackFn(details) {
        return {
            authCredentials: {
                username: "14ae212b29a2a",
                password: "d160bc0854"
            }
        };
    }

    chrome.webRequest.onAuthRequired.addListener(
        callbackFn,
        {urls: ["<all_urls>"]},
        ['blocking']
    );