google.maps.event.addListener(infowindow, "closeclick", function() {
    // The API function doesn't have the e parameter, I can't access closeclick
});

container.addEventListener('click', function(ev) {
    if (ev.target.src == 'https://maps.gstatic.com/mapfiles/api-3/images/mapcnt6.png') {
        return false;
    }
    // the code I want to execute only when the click event doesn't come from the InfoWindow
});

google.maps.event.addListener(infowindow, "closeclick", function(e) {
   e.stopPropagation();
});

var aListener = google.maps.event.addListener(map, 'click', function(event) {
    // Try to prevent event propagation to the map
    event.stop();
    event.cancelBubble = true;
    if (event.stopPropagation) {
        event.stopPropagation();
    }
    if (event.preventDefault) {
        event.preventDefault();
    } else {
        event.returnValue = false;
    }
});