renderOutsideViewport => false breaks Carousel rendering

[mkhatib]

As far as I can tell this is recent behavior but maybe has been there for awhile.

Reproduce:

1. Run local server
2. Open carousel example
3. Navigate the carousel or the slider to jump to the YouTube element
4. Notice that it will never be scheduled for rendering and hence the iframe is never created (You'll only see the thumbnail placeholder).

Tested this with amp-vine which seems to have the same behavior when renderOutsideViewport => false, i.e. it won't render in the carousel.

Dropping the renderOutsideViewport seems to fix this though haven't done a lot of debugging to pinpoint what is the problem.

[mkhatib]

More debugging shows that isInViewport returns false when the element is actually in the viewport.

[mkhatib]

Found the problem. Both carousel and slider were scheduling layouting before they update that the slide is now in viewport. Changing the order fixes it.