Covert Base64 image to blob and back to Base64

HTML

<h1>Create an image/png blob, then fetch it with XHR</h1>
  <a href="https://bl.ocks.org/nolanlawson/0eac306e4dac2114c752">Source</a>
  <pre id="display"></pre>
  <script src="index.js"></script>

JavaScript

(function () {
  'use strict';
  
  // From http://stackoverflow.com/questions/14967647/ (continues on next line)
  // encode-decode-image-with-base64-breaks-image (2013-04-21)
  function fixBinary (bin) {
    var length = bin.length;
    var buf = new ArrayBuffer(length);
    var arr = new Uint8Array(buf);
    for (var i = 0; i < length; i++) {
      arr[i] = bin.charCodeAt(i);
    }
    return buf;
  }

  var display = document.getElementById('display');
  display.innerHTML = (display.innerHTML || '');
  function log(text) {
    display.innerHTML += "\n" + text;
  }  
  var base64 = 
   ...