Codebase Browser
chromium
Go to App

chromium/third_party/blink/web_tests/external/wpt/html/editing/dnd/draggable-areas/border.html 

<!DOCTYPe html>
<meta charset='utf-8'>
<title>drag and drop – draggable areas – border</title>
<style>
a {
  display: block;
  height: 200px;
  width: 200px;
  background-color: blue;
  border: 10px solid orange;
}
</style>

<p>Try dragging the orange border of the blue box below, in a downwards direction. It should be draggable.</p>

<a href='#' draggable="true" ondragstart="event.dataTransfer.effectAllowed ='copy'"></a>