What you could do is add a CSS rule to your main CSS-file, like:
.googleMapsWidget > div {
height: 100vh !important;
}
If you add this kind of rule to your googlemapswidget.css than you can ommit the '!important'.
This will only work for the div the GoogleMaps widget is in, though. So if you only display that on a page, you should be fine. When you have two tables of whatever, the GoogleMapswidget will only be as high as the table it is in...
See also:
http://stackoverflow.com/questions/1575141/make-div-100-height-of-browser-window