title: CSS - infinite animation (moving to right loading gradient) is flickering
body: <p>I was following this tutorial here: <a href="https://cloudcannon.com/deconstructions/2014/11/15/facebook-content-placeholder-deconstruction.html" rel="noreferrer">https://cloudcannon.com/deconstructions/2014/11/15/facebook-content-placeholder-deconstruction.html</a></p>
  
  <p>to create a dummy loader. unfortunately this tutorial includes fixed pixel-values and I want it to work on screens of all sizes. so I adjusted the animation like this:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>@keyframes placeHolderShimmer {
    0% {
      background-position: -30vw 0
    }
    100% {
      background-position: 30vw 0
    }
  }
  
  .c-animated-background {
    animation-duration: 1.5s;
    animation-fill-mode: forwards;
    animation-iteration-count: infinite;
    animation-name: placeHolderShimmer;
    animation-timing-function: linear;
    background: fff;
    background: linear-gradient(to right, #eeeeee 8%, #dddddd 18%, #eeeeee 33%);
    height: 100%;
    width: 100%;
    position: relative;
    padding-top: 50px;
    -webkit-backface-visibility: hidden
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  
  &lt;head&gt;
    &lt;link rel="stylesheet" href="style.css"&gt;
    &lt;script src="script.js"&gt;&lt;/script&gt;
  &lt;/head&gt;
  
  &lt;body class="c-animated-background"&gt;
  &lt;/body&gt;
  
  &lt;/html&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>Unfortunately on animation end after 1.5s, the grey area jumps either forward or back, depending on the keyframe-background-position values that I set. How can I prevent that and make the transition smooth? also, the animation seems to be more intense on the performance than I thought - when I want to inspect the background-element in dev mode in chrome with my macbook 2016', it hangs for around 15 seconds. should I perhaps use a transition/transform-animation instead?</p>
  
  <p>Here is a plunker: <a href="https://plnkr.co/edit/X8PBIUYmAC11LCUV9uTy?p=preview" rel="noreferrer">https://plnkr.co/edit/X8PBIUYmAC11LCUV9uTy?p=preview</a></p>