<!DOCTYPE html> <style> ::-webkit-scrollbar { width: 20px; height: 30px; background-color: blue; } </style> <script src="../../resources/run-after-layout-and-paint.js"></script> <script> if (window.testRunner) { testRunner.waitUntilDone(); testRunner.dumpAsText(); } runAfterLayoutAndPaint(function() { var content = document.getElementById('content'); content.style.height = '1000px'; runAfterLayoutAndPaint(function() { content.style.width = '1000px'; runAfterLayoutAndPaint(function() { if (window.testRunner) testRunner.notifyDone(); }); }); }); </script> Tests adding composited horizontal custom scrollbar then the vertical scrollbar. Passes if no assertion failure. <div style="overflow: auto; width: 500px; height: 500px; backface-visibility: hidden"> <div id="content" style="width: 400px; height: 400px"></div> </div>