title: CardView dynamic shadow depends not only on elevation
body: <p>While developing my app I'd created a RecyclerView with expandable CardViews inside and then mentioned <em>"hey, why does the elevation is changing a bit while I'm animating only vertical size of card and opacity of extension?"</em>.</p>
  
  <p>And then I've found what it's not an elevation who chages -- it's only a shadow changed.</p>
  
  <p>Does anybody heard smth about it? Is it just an undescribed thing of interface drawing? I have no objections for cool feature, but it just a bit confused me (I've even spend about an hour to find out something about it on Google's guidelines)</p>
  
  <p>I've shared the code that proves the idea of "height affects shadow drawing" but share some information if theres' something more behind this.</p>