title: JavaScript not being properly executed in HtmlUnit
body: <p>I'm currently developing some tests with HtmlUnit.  It's loading a page that contains braintree.js (their form encryption library).  I have a bunch running, but I'm stuck where it calls crypto.  The JS in question is:</p>
  
  <pre><code>  (function() {
          try {
              var ab = new Uint32Array(32);
              crypto.getRandomValues(ab);
              sjcl.random.addEntropy(ab, 1024, "crypto.getRandomValues");
          } catch (e) {}
      })();
  </code></pre>
  
  <p>HtmlUnit is throwing: </p>
  
  <pre><code>EcmaError, ReferenceError, "'crypto' is not defined."
  </code></pre>
  
  <p>I suppose HtmlUnit doesn't include crypto.  Would it be possible to include a crypto library myself?</p>