burlesco/src/background.js

// Script blocking
chrome.webRequest.onBeforeRequest.addListener(
    function(details) {
        return {cancel: true};
    },
    {
        urls: [
            // O Estado de S. Paulo
            "*://*.estadao.com.br/paywall/*",

            // Folha de S.Paulo
            "*://paywall.folha.uol.com.br/*",
            "*://static.folha.uol.com.br/paywall/*",

            // O Globo
            "*://ogjs.infoglobo.com.br/*/js/controla-acesso-aux.js",
            "*://cdn.tinypass.com/api/tinypass.min.js",

            // Gazeta do Povo
            "*://*.gazetadopovo.com.br/conta/public/js/connect_api.js*",
            "*://*.gazetadopovo.com.br/conta/going/api/paywall/*",

            // Zero Hora
            "*://zh.clicrbs.com.br/it/js/paid-content-config.js*",
            "*://www.rbsonline.com.br/cdn/scripts/paywall.min.js*",

            // Correio Popular
            "*://correio.rac.com.br/includes/js/novo_cp/fivewall.js*",

            // O Estado do Maranhão
            "*://dashboard.tinypass.com/xbuilder/experience/load*",
            "http://assets.imirante.com/2.0/oestadoma/js/jquery.login.min.js",

            // Jornal de Novo Hamburgo
            "*://www.jornalnh.com.br/includes/js/paywall.js*",
            "*://blockv2.fivewall.com.br/*"
        ],
        types: ["script"]
    },
    ["blocking"]
);

// XHR blocking
chrome.webRequest.onBeforeRequest.addListener(
    function(details) {
        return {cancel: true};
    },
    {
        urls: [
            // Diário Catarinense
            "http://dc.clicrbs.com.br/jornal-2015/jsp/paywall.jspx*",

            // Jornal de Santa Catarina
            "http://jornaldesantacatarina.clicrbs.com.br/jornal/jsp/paywall*",

            // O Globo
            "*://cdn.tinypass.com/api/tinypass.min.js"
        ],
        types: ["xmlhttprequest"]
    },
    ["blocking"]
);

// Cookie injection
chrome.webRequest.onBeforeRequest.addListener(
    function(details) {
        chrome.cookies.remove({
            'url': 'http://jota.info/*',
            'name': 'articles'
        });
    },
    {
        urls: [
            // JOTA
            "http://jota.info/*"
        ],
        types: ["main_frame"]
    }
);

// Referer injection
function insertHeader(name, value, requestHeaders) {
    /**
     * @param {string} name - Name of the header to be inserted
     * @param {string} value - Value of the header to be inserted
     * @param {Object[]} requestHeaders - Provided by webRequest
     *     listeners in callback arg `details.requestHeader`
     * @param {string} requestHeaders[].name
     * @param {string} requestHeaders[].value
     */
    var headerIndex = requestHeaders.findIndex(x => x.name == name);

    var newHeader = {name: name, value: value};
    if (headerIndex == -1)
        requestHeaders.push(newHeader);
    else
        requestHeaders[headerIndex] = newHeader;
}

chrome.webRequest.onBeforeSendHeaders.addListener(
    function(details) {
        var headers = ['Referer'];

        //if (/https?:\/\/access\.nexojornal\.com/.test(details.url))
            //headers.push('X-Article-Referrer')

        headers.forEach(header =>
            insertHeader(
                header,
                'https://www.google.com.br/',
                details.requestHeaders
            )
        );

        return {requestHeaders: details.requestHeaders};
    },
    {
        urls: [
            // Nexo
            //"*://access.nexojornal.com.br/access/content/*",

            // Financial Times
            "*://www.ft.com/*"
        ],
        types: ["xmlhttprequest", "main_frame"]
    },
    ["blocking", "requestHeaders"]
);