anchor.diff:  var canvas = document.getElementById('canvas');
   var videoStream = null;
   var preLog = document.getElementById('preLog');
  +var stopButton = document.getElementById('buttonStop');
  +var snapButton = document.getElementById('buttonSnap');
  +var startButton = document.getElementById('buttonStart');
  +
  +function buttonState(b, s) {
  +	if (b) b.disabled = s;
  +}
   
   function log(text)
   {
  
positive.code: 
  function stop()
  {
  	var myButton = document.getElementById('buttonStop');
  	if (myButton) myButton.disabled = true;
  	myButton = document.getElementById('buttonSnap');
  	if (myButton) myButton.disabled = true;
  	if (videoStream)
  	{
  		if (videoStream.stop) videoStream.stop();
  
negative.code: 	}
  	else if (window.URL) video.src = window.URL.createObjectURL(stream);
  	else video.src = stream;
  	buttonState(snapButton, false);
  	buttonState(stopButton, false);
  }
  
  function start()
  