you can make your div fullscreen by using the javascript screen object.
try the following code
include jquery in your markup
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.11.2/jquery.min.js"></script>
$(function(){
$('#map-canvas').css('width',screen.width);
$('#map-canvas').css('height',screen.height);
});
hope this may help you.