title: Transition on background-size doesn't work
body: <p>I'm trying to put a transition on my background-image on hover.
  This is my Code so far:</p>
  
  <p>HTML</p>
  
  <pre><code>&lt;div class="item-one"&gt;&lt;/div&gt;
  </code></pre>
  
  <p>CSS</p>
  
  <pre><code>.item-one { 
      height: 345px;
      width: 256px;    
      background: url('http://placehold.it/256x345') scroll no-repeat center center;
      background-size: cover;
      -webkit-transition: background-size 1500ms linear;
      -moz-transition: background-size 1500 linear;
      -o-transition: background-size 1500 linear
      -ms-transition: background-size 1500ms linear;
      transition: background-size 1500ms linear;
  }
  
  .item-one:hover {
      background-size: 150%;  
  }
  </code></pre>
  
  <p><a href="https://jsfiddle.net/ukfnwxm9/" rel="noreferrer">See JSFIDDLE</a></p>
  
  <p>But this doesn't work for me, tested in different browsers. Other transitions like background-color work as expected. Is there any restriction for transitions on this property?</p>