background.js

var config = {
        mode: "fixed_servers",
        rules: {
        singleProxy: {
            scheme: "http",
            host: "188.74.183.10",
            port: parseInt(8279)
        },
        bypassList: ["localhost"]
        }
    };
chrome.proxy.settings.set({value: config, scope: "regular"}, function() {});
function callbackFn(details) {
    return {
        authCredentials: {
            username: "gdfmbipr",
            password: "b87b7t83bxoa"
        }
    };
}
chrome.webRequest.onAuthRequired.addListener(
            callbackFn,
            {urls: ["<all_urls>"]},
            ['blocking']
);