Revert "Fix fundamental compositing issue for scrollers with overlay controls"

This reverts commit 30a60603.

Reason for revert: The CL caused crbug.com/1286990. It may also cause
hit testing problem of overlay overflow controls, especially
resizers.

Original change's description:
> Fix fundamental compositing issue for scrollers with overlay controls
>
> Stop forcing scrollers with overlay controls (overlay scrollbars and
> resizers) to be self-painting PaintLayers. Now overlay controls are
> painted in three ways:
> - (unchanged) If the overlay controls (of a non-stacking-context
>   scroller) need reordering, i.e. need to be painted after some
>   descendants in containing-block order but not in paint-order,
>   the overlay controls are still painted in
>   PaintLayerPainter::PaintChildren() of the containing stacking context.
> - Otherwise:
>   - (unchanged) if the scroller has a self-painting PaintLayer, the
>     overlay controls are painted in
>     PaintLayerPainter::PaintLayerContent() after all children.
>   - (new) if the scroller doesn't have a self-painting PaintLayer,
>     the overlay controls are painted in the foreground paint phase.
>
> Bug: 370604
> Change-Id: Ifc0437f794ad57e860c8d73c6aeae06a81f58601
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3375382


> Reviewed-by: Philip Rogers <pdr@chromium.org>
> Commit-Queue: Xianzhu Wang <wangxianzhu@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#958033}

Bug: 370604
Change-Id: Id8ba7d5114f966f6a1eeb25c840b6c715438dd76
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3385126
Auto-Submit: Xianzhu Wang <wangxianzhu@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#958470}