title: ember tests passing in chrome, not in phantomjs
body: <p>I have tests for <a href="https://github.com/shaunc/ember-grid" rel="nofollow noreferrer">an addon</a> which pass in chrome, but fail in phantomjs.</p>
  
  <p>It seems to be a problem similar to <a href="https://stackoverflow.com/questions/31837891/ember-acceptance-test-failing-in-phantomjs-but-passing-in-chrome">this question</a>. However, I tried the solution there and it didn't work for me.</p>
  
  <p>The code is all available in the public repo linked above. The failures are exhibited in the failing travis build on github. Any ideas on how to diagnose better and fix?</p>
  
  <p><strong>EDIT</strong> -- actual error message </p>
  
  <hr>
  
  <pre><code>        Died on test #1     at http://localhost:7357/assets/test-support.js:3062
              at test (http://localhost:7357/assets/test-support.js:1945)
              at test (http://localhost:7357/assets/dummy.js:2090)
              at http://localhost:7357/assets/dummy.js:2885
              at http://localhost:7357/assets/vendor.js:150
              at tryFinally (http://localhost:7357/assets/vendor.js:30)
              at http://localhost:7357/assets/vendor.js:156
              at http://localhost:7357/assets/test-loader.js:29
              at http://localhost:7357/assets/test-loader.js:21
              at http://localhost:7357/assets/test-loader.js:40
              at http://localhost:7357/assets/test-support.js:6775: Can't find variable: Symbol
  </code></pre>
  
  <hr>
  
  <p><strong>UPDATE</strong></p>
  
  <p>Following up on a hint from @knownasilya, I tried forcing optional babel transform <code>es6.spec.symbols</code> on: in <code>ember-cli-build.js</code>:</p>
  
  <pre><code> module.exports = function(defaults) {
     var app = new EmberAddon(defaults, {
       // Add options here
  +    babel: {
  +      optional: ['es6.spec.symbols']
  +    }
     });
  </code></pre>
  
  <p>However -- no luck. It does look like an es6 transpilation problem, though. Did I not pass the option successfully? Any other hints? I'll be happy to post code snippets if you don't want to look in the repo. :)</p>
  
  <p><strong>UPDATE 2</strong></p>
  
  <p>Including as well:</p>
  
  <pre><code>+      includePolyfill: true
  </code></pre>
  
  <p>works!</p>
  
  <p>Now I'm on to:</p>
  
  <pre><code>        ReferenceError: Can't find variable: requestAnimationFrame
  </code></pre>
  
  <p>I'm looking for a polyfill for this as well... but looking at the testem configuration for <code>ember-collection</code>, which seems to have a similar configuration, I notice that phantomjs testing is turned off! Now the question is: best way to test <code>requestAnimationFrame</code> in phantomjs?</p>