Tools/TestWebKitAPI/Tests/WebKitCocoa/contenteditable-user-select-user-drag.html

<!DOCTYPE html>
<html>
<meta name="viewport" content="width=device-width">
<head>
<style>
    body, html {
        width: 100%;
        height: 100%;
    }

    body {
        margin: 0;
    }

    #editor {
        width: 200px;
        height: 200px;
        outline: 1px solid black;
    }

    #draggable {
        background-color: red;
        width: 200px;
        height: 200px;
        -webkit-user-select: all;
        -webkit-user-drag: element;
        display: inline-block;
    }
</style>
</head>

<div id="draggable" draggable="true">This text should not be draggable without a red background.</div>
<div id="editor" contenteditable=""></div>

<div><code>To manually test, attempt to drag the colored block.</code></div>

<script>
draggable.addEventListener("dragstart", event => {
    event.dataTransfer.setData("text/plain", "Text");
});
</script>
</html>