result: undefined При попытке взаимодействия с DOM Chrome Extension

Код background js:

chrome.browserAction.onClicked.addListener(function(tab){
    chrome.tabs.sendMessage(tab.id, {
        command: "change_smth",
        title: "hoge"
    },
    function(msg){
        console.log("result:", msg)
    });
});  

Код script js:

chrome.runtime.onMessage.addListener(function(msg, sender, sendResponse) {
    if (msg.command && (msg.command == "change_title")) {
        var src = document.getElementsByTagName("title")[0].innerHTML;
        var dst = msg.title;
        document.getElementsByTagName("title")[0].innerHTML = dst;
        sendResponse("the page title's changed: '" + src + "' -> '" + dst + "'");
    }
});

Код manifest json:

{
    "name":"DOM",
    "manifest_version": 2,
    "description":"manipulations",
    "version":"1.0",
    "content_scripts": [
        {
            "matches":[
                "<all_urls>"
            ],
            "js": ["script.js", "jquery.js"]
        }
    ],
    "background": {
        "scripts":["background.js", "jquery.js"]
    },
    "browser_action": {
        "default_icon": "icon.png"
    },
    "permissions": [
        "tabs"
    ]
}

Буду очень благодарен, если подскажите, в чём ошибка.