At webkit r245059, we sometimes assert at ASSERT(!parentClipRect.isInfinite()) in RenderLayerBacking::computeParentGraphicsLayerRect. I can reproduce this in DumpRenderTree with accessibility/media-element.html
This code runs when we have a m_ancestorClippingLayer, and we make one based on the result of RenderLayerCompositor::clippedByAncestor(), which uses: layer.backgroundClipRect(RenderLayer::ClipRectsContext(computeClipRoot, TemporaryClipRects)).isInfinite() However, RenderLayerBacking::computeParentGraphicsLayerRect() is doing: ShouldRespectOverflowClip shouldRespectOverflowClip = compositedAncestor->isolatesCompositedBlending() ? RespectOverflowClip : IgnoreOverflowClip; RenderLayer::ClipRectsContext clipRectsContext(compositedAncestor, TemporaryClipRects, IgnoreOverlayScrollbarSize, shouldRespectOverflowClip); LayoutRect parentClipRect = m_owningLayer.backgroundClipRect(clipRectsContext).rect(); // FIXME: Incorrect for CSS regions. so 'shouldRespectOverflowClip' differs.
That code came from https://trac.webkit.org/changeset/168314/webkit
*** This bug has been marked as a duplicate of bug 197695 ***