chromium/third_party/blink/manual_tests/user-drag-with-decorations.html

This tests that we don't include overflow decorations from our ancestor nodes in the drag image for -webkit-user-drag: element.  To perform this test drag the green square below.  The drag image should not contain any parts of the scrollbar graphics visible on the page.

<div style="height:100px; width:100px;overflow:scroll;">
    <div style="-webkit-user-drag:element;position:absolute; background: rgba(0,128,0,0.5); height:100px; width:100px;">
        Drag me!
    </div>
</div>