RequestAnimationFrame block by media(img, background etc.) rendering

[chestnutchen]

Env:
iOS webkit
A mediocre network traffic

Problem:
Found the issue that slide animation lost a lot of frames when page is almost loaded and ui thread is painting some media elements such as img tag or CSS background.

Some info:
Dived into performance debugging and found the requestAnimationFrame was delayed by nothing. But it took 50ms, 100ms or even more time to do next moveAnimateUpdate detecting by console.log. The issue could be reproduced in the demo page without page cache in a mediocre network traffic.

[rcbyr]

Thank you very much. I will investigate this behavior and will create a fix.

[rcbyr]

At the moment, I don't think there is a performance problem with the slider. Therefore, I am closing this issue for the moment.