Bug 186996

If the browser window is made hidden and then visible, animations created with Web Animation API are not resumed.

Example: https://codepen.io/anon/pen/eKjgyo

Steps to reproduce:

1. Set up an infinite animation like this:

  var animation = document.getElementById("box").animate([
    { transform: 'rotate(0deg)', offset: 0 },
    { transform: 'rotate(270deg)', offset: .5 },
    { transform: 'rotate(0deg)', offset: 1 }
  ], {
    duration: 3000,
    iterations: Infinity,
    easing: 'linear',
    delay: 0
  });

2. Ensure that the animation rotates the element.
3. Hide the browser window by pressing the orange '-' minimize button or by pressing Command-M.
4. Bring the window visible by clicking it in the dock.
5. The element should still be rotating.

Expected Result:
After bringing the window visible in step 4, the element should still be rotating.

Actual Results:
The element is no longer rotating.

It seems that simply dragging another window on top of the browser window will have the same effect as minimizing. I tested also CSS animations, and they are resumed correctly. I would expect Web Animations to behave the same way.

Build: Release 59 (Safari 12.0, WebKit 13606.1.21)