See https://codereview.chromium.org/2825343003/diff/1/third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp#newcode859 for the original CL that I forked this bug from.

Currently if you modify layout inside a scrollable area such that you change where a sticky should be, *without* modifying the sticky element itself or its subtree, we don't invalidate the sticky constraints. This means that stale constraints can be used.

See https://codereview.chromium.org/2825343003/diff/1/third_party/WebKit/LayoutTests/fast/css/sticky/sticky-position-works-with-scroll-apis.html for some examples that would not work under the current code.

Instead, we should invalidate sticky constraints during PaintLayerScrollableArea::UpdateAfterLayout.