Untitled

{
    "manifest_version": 2,
    "name": "Such Activity",
    "description": "Wow",
    "version": "1.0",
    "permissions": ["tabs", "<all_urls>"],
    "browser_action": {
        "default_icon": {
            "19": "images/icons/19.png",
            "38": "images/icons/38.png"
        },
        "default_popup": "popup.html"
    },
    "icons": {
        "16": "images/icons/16.png",
        "19": "images/icons/19.png",
        "38": "images/icons/38.png",
        "64": "images/icons/64.png",
        "128": "images/icons/128.png"
    }
}

function injectTheScript() {
        chrome.tabs.query({active: true, currentWindow: true}, function(tabs) {
        // query the active tab, which will be only one tab
        //and inject the script in it
        chrome.tabs.executeScript(tabs[0].id, {file: "content_script.js"});
    });
}
document.getElementById('clickactivity').addEventListener('click', injectTheScript);

function clickSome() {
    function getElementsByText(text) {
        function rec(ele, arr)
        {
            if (ele.childNodes.length > 0)
                for (var i = 0; i < ele.childNodes.length; i++)
                    rec(ele.childNodes[i], arr);
            else if (ele.nodeType == Node.TEXT_NODE &&
                     ele.nodeValue.indexOf(text) != -1)
                arr.push(ele.parentNode);
            return arr;
        }
        return rec(document.body, []);
    }
    var x = 'Text';
    var my = getElementsByText(x.ignoreCase);
    var mod =my[0];
    console.log(my);
    document.getElementsByClassName(mod)[0].click();
}
clickSome();

<!doctype html>
<html>
    <head><title>activity</title></head>
<body>
    <button id="clickactivity">click</button>
    <script src="popup.js"></script>
</body>
</html>