Multiuser Sketchpad add for window.onresize event.

function onResize() { 
  var new_height = window.innerHeight; 
  messages.style.height = (new_height - 132) + 'px'; 
  panel.style.height = new_height + 'px'; 
} 

window.onresize = onResize;

onResize();

Suggestion for canvas resizing problem

Resizing the canvas is a problem since if the window is small, and resized to be big, resizing the canvas will stretch the picture.

Solution is to init with a really big canvas (ie 1920x1080), since without scrollbars it'll be hidden until resizing the window.