Chrome Extensions send message from content scripts to background. -> http://kuroeveryday.blogspot.jp/2015/06/ChromeExtensionssendMessage.html

background.js

chrome.runtime.onMessage.addListener(
    function (request, sender, sendResponse) {
        switch (request.type) {
            case 'add':
                add(request.value, sendResponse);
                break;
            case 'search':
                search(request.value, sendResponse);
                break;
            default:
                console.log('typeがわかんないよ');
                console.log(request);
                break;
            }
        }
    );

function add(value, callback) {
    // ここで登録処理
    console.log('background:add_' + value);
    callback("add:" + value);
}

function search(value, callback) {
    // ここで検索処理
    console.log('background:search_' + value);
    callback("search:" + value);
}

content_script.js

var title = document.getElementsByClassName('post-title entry-title')[0].innerText;

chrome.runtime.sendMessage(
    {
        type: "add",
        value: title
    },
    function (response) {
        if (response) {
            alert(response);
        }
    }
    );


chrome.runtime.sendMessage(
    {
        type: "search",
        value: title
    },
    function (response) {
        if (response) {
            alert(response);
        }
    }
    );

manifest.json

{
    "name": "ContentScriptとBackgroundの通信テスト",
    "version": "0.0.1",
    "manifest_version": 2,
    "description": "ContentScriptとBackgroundをsendMessegaやonMessegeで通信できるか確認する",
    "background": {
        "scripts": ["./background.js"]
    },
    "content_scripts": [
        {
            "matches": ["http://kuroeveryday.blogspot.jp/*"],
            "js": ["./content_script.js"]
        }
    ]
}