title: Firebase getDownloadURL() is really slow at getting image URLs
body: <p>I have a page which displays multiple (12+) objects in components, each of which has an image. This image has a <code>src</code> attribute, which I'm setting via a call to my Firebase storage:</p>
  
  <pre><code>this.props.storage.child('Land.jpg').getDownloadURL().then(function(url) {
              var img = document.getElementById('imageGoesHere'+this.state.currentId);
              img.src = url;
          }.bind(this))
  </code></pre>
  
  <p>The <code>storage</code> prop is generated and passed down by a parent component:</p>
  
  <pre><code>firebase.initializeApp(config);
  var storage = firebase.storage();
  var storageRef = storage.ref("");
  </code></pre>
  
  <p>The <code>storageRef</code> var is passed as a prop to each child component that calls the <code>getDownloadURL()</code> function.</p>
  
  <p>This works, but the <code>getDownloadURL</code> function seems to be really slow. The page renders, and then each image takes at least a second to be shown/rendered. I know it's not the raw URL's issue, since I can get the raw URL and paste it into the <code>src</code> and it loads fine (i.e. nearly instantly); I look at the Network tab in chrome devtools and it shows at least a second between the <code>getDownloadURL</code> call and the response. Is this the proper way of getting images to be shown in web pages? The Firebase Storage docs don't mention any other way. </p>
  
  <p>edit: Two things; firstly I only have 5 test images in the storage, so it's not like I'm syncing to a whole bunch with the root storage ref. </p>
  
  <p>Second thing; chrome devtools shows me that it's "stalling" for 1-4 seconds, and the actual request only takes 100ms tops. What can cause stalling?</p>