tab_comm_main.js

// load in our tools
var tabs = require("tabs");
var data = require("self").data;

// when someone goes to a tab:
tabs.on('activate', function(tab){
    tab.attach({
        // attach the tab.js file
        contentScriptFile: data.url("tab.js"),
        // and handle messages coming FROM tab.js
        onMessage: function(data){
            if(data.type == "click"){
                // do some stuff, then post back to the tab
                this.postMessage({
                    "type": "click_complete",
                    "msg": "thanks for clicking the button!"
                });
            }else{
                console.log("unknown message from TAB: " + data.toSource());
            }
        }
    });
});