Merge 127520 - REGRESSION(r120832): RenderLayer::clampScrollOffset doesn't properly clamp

Merge 127520 - REGRESSION(r120832): RenderLayer::clampScrollOffset doesn't properly clamp
https://bugs.webkit.org/show_bug.cgi?id=95776

Reviewed by Simon Fraser.

.:

* ManualTests/select-menu-list-wrongly-positioned.html: Added.

Source/WebCore:

r120832 consolidated the clamping logic into RenderLayer::clampScrollOffset. The existing code wouldn't properly ensure that
the offset were positive which got exposed to other code paths, leading to the regression.

Tested by ManualTests/select-menu-list-wrongly-positioned.html as I didn't find a way to create a reliable layout test.

* rendering/RenderLayer.cpp:
(WebCore::RenderLayer::clampScrollOffset):
Fixed the clamping logic to ensure that the scroll offset's dimensions are positive.


TBR=jchaffraix@webkit.org
Committed: https://trac.webkit.org/changeset/127545