[Webkit-unassigned] [Bug 211431] New: [WinCairo] CSS animations break raf sequence

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=211431

            Bug ID: 211431
           Summary: [WinCairo] CSS animations break raf sequence
           Product: WebKit
           Version: WebKit Nightly Build
          Hardware: Unspecified
                OS: Windows 10
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebCore Misc.
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: pfeldman at chromium.org

Creating a simple CSS animation fires random rafs every 2-20ms. In some of these rafs animated element is not moving. See console for the following snippet:

<style>button { transition: margin 500ms linear 0s; margin-left: 0; }</style>
<button id=button>Hello</button>

<script>
requestAnimationFrame(foo);
let lastFrame = performance.now();
function foo(time) {
  console.log(time - lastFrame);
  lastFrame = time;
  console.log(button.getBoundingClientRect().x);
  if (button.getBoundingClientRect().x < 100)
    requestAnimationFrame(foo);
}
setTimeout(() => {
  button.style.marginLeft = "100px";
});
</script>

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