RenderSVGRoot::layout() -> m_resourcesNeedingToInvalidateClients -> resource->removeAllClientsFromCache() -> RenderSVGResourceContainer::markAllClientsForInvalidation -> RenderSVGResourceContainer::markAllClientLayersForInvalidation -> invalidateStyleAndLayerComposition -> dirty style -> schedule style recalc. This leads to unstable layout.
<rdar://problem/60306128>
Alternatively split RenderSVGResourceContainer::markAllClientsForInvalidation into 2 functions and call invalidation only through the non-layout case (e.g. make sure this function never gets called while in layout)