finally it works

chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) {
    console.log(sender.tab.url);

    if (message.greeting == "info") {
        alert('recideved "' + message.greeting + '" in background');

        var i, recieved_data = JSON.stringify(message.data);
        var amount = message.amount;
        alert('RECIEVED:' + recieved_data);

        //for (i = 0; i < recieved_data.length)


        chrome.tabs.create({
            active: false, url: 'http://www.editpad.org/'
        }, function(tab) {
            chrome.tabs.executeScript(tab.id, {
                //var serialized_data = JSON.stringify(recieved_data);
                code: 'document.getElementById("text").value = ' + recieved_data,
            }, function(result) {
                if (!result || null == result) {
                    alert('Failed to run content script.\n' + chrome.runtime.lastError.message);
                    return;
                }
                alert('you typed: "' + result[0] + '"');
            });
        });

        //sendResponse({farewell: "welldone"});
    }
});






function get_specific_stuff(name) {
    var i, tmp, text_to_send, results;

    results = document.getElementsByClassName(name);
    alert('num' + results.length);

    text_to_send = '';
    for (i = 0; i < results.length; i++) {
        text_to_send += results[i].innerHTML;
    }
    alert('SENT: ' + text_to_send);

    chrome.runtime.sendMessage({greeting: "info", data: text_to_send, amount: results.length}, function(response){});
}

function access_page_stuff(text) {
    var name = "bibtex";
    get_specific_stuff(name);
}

chrome.extension.onMessage.addListener(function(message, sender, sendResponse) {
    switch (message.type) {
        case "start":
            access_page_stuff(message.text);
        break;
    }
});

/*
chrome.runtime.onMessage.addListener( function(message, sender, sendResponse) {
    switch (message.type) {
        case "start":
            alert('recieved message 2');
            get_stuff_from_page(message.text);
    }
});*/