Read the documentation of chrome.runtime.onMessage:
function sendResponse
Function to call (at most once) when you have a response. The argument should be any JSON-ifiable object. If you have more than one onMessage listener in the same document, then only one may send a response. This function becomes invalid when the event listener returns, unless you return true from the event listener to indicate you wish to send a response asynchronously (this will keep the message channel open to the other end until sendResponse is called).
chrome.runtime.onMessage.addListener(function(request, sender, sendResponse){
chrome.tabs.query({active: true, currentWindow: true}, function(tabs){
var requests = getTabRequests(tabs[0].id);
//getTabRequests gets all the information i stored about a tab
sendResponse({requests: requests});
});
return true; // <-- Required if you want to use sendResponse asynchronously!
});
(chrome.extension.onMessage is deprecated, use chrome.runtime.onMessage instead, the former is an alias of the latter though.)
