title: element with border-radius and overflow hidden can't clip contents with position absolute which it is not the element's direct child
body: <p>In Chrome 60.0.3112.90(64-bit).
  My system is macOS 10.12.4
  <a href="https://i.stack.imgur.com/W8fNE.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/W8fNE.png" alt="enter image description here"></a></p>
  
  <p>As you can see, the blue box is overflow. How can I solve this problem? And why does it overflow?</p>
  
  <p>Please check this <a href="https://jsfiddle.net/1w8rsz42/6/" rel="nofollow noreferrer"><strong>JSFiddle</strong></a></p>
  
  <p>or this is my code.</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>.outer {
    width: 200px;
    height: 200px;
    border-radius: 10px;
    border: 1px solid black;
    position: absolute;
    overflow: hidden;
  }
  
  .inner {
    width: 200px;
    height: 200px;
    position: relative;
    overflow: scroll;
    background-color: lightblue;
  }
  
  .inner2 {
    width: 200px;
    height: 400px;
    background-color: lightgray;
  }
  
  .inner3 {
    width: 200px;
    height: 100px;
    position: absolute;
    background-color: blue;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div class="outer"&gt;
    &lt;div class="inner"&gt;
      &lt;div class="inner2"&gt;
        &lt;div class="inner3"&gt;&lt;/div&gt;
      &lt;/div&gt;
    &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>