title: Caret position when centering with flexbox in contenteditable
body: <p>Tested on OSX Chrome 45, <code>align-items: center;</code> is working for content, but if you click into the empty editable below, the caret position is not centered until you start typing.</p>
  
  <p>Is the only way to fix this with top/bottom balanced padding or is there a way of getting this to work without pixel shifting? Thanks</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>[contenteditable="true"] {
      border: 1px solid #ddd;
      display: flex;
      align-items: center;
      min-height: 46px;
  }
  
  [contenteditable="true"]:focus {
      outline: none;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;div contenteditable="true"&gt;&lt;/div&gt;
  &lt;div contenteditable="true"&gt;content is centered, but caret isn't&lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>