Bug 308303 – [threaded-animations] failed assertion `ASSERT(sourceScrollableArea->scrollingNodeID())` in `ScrollTimeline::computeProgressResolutionData()`

• Status: RESOLVED
• Resolution: FIXED
• Component: Animations

[Antoine Quint]

We have reports of `ASSERT(sourceScrollableArea->scrollingNodeID())` in `ScrollTimeline::computeProgressResolutionData()` failing.

Code inspection make it pretty obvious what is wrong: we use `ScrollTimeline::canBeAccelerated()` to determine that a timeline can be accelerated in `AcceleratedEffectStackUpdater::takeTimelinesUpdate()` to guard calls to `ScrollTimeline::updateAcceleratedRepresentation()` and then `ScrollTimeline::computeProgressResolutionData()`, letting those methods imply that they have a source with a scrolling node ID.

However, `ScrollTimeline::canBeAccelerated()` is not live and returns the cached result of `ScrollTimeline::computeCanBeAccelerated()` under `AnimationTimeline::runPostRenderingUpdateTasks()` so that we can determine when that status changes one per animation frame.

We need to change `canBeAccelerated()` to be live and keep and rename the cached flag for just that purpose.

[Antoine Quint]

rdar://168255217

[Antoine Quint]

Pull request: https://github.com/WebKit/WebKit/pull/59093

[EWS]

Committed 307965@main (05c889923120): <https://commits.webkit.org/307965@main>

Reviewed commits have been landed. Closing PR #59093 and removing active labels.