Struct ContainerRecord 

struct ContainerRecord {
    contributing_nodes: FxHashSet<OpaqueNode>,
    painted_region: PaintedRegion,
    last_painted_element: Option<OpaqueNode>,
}

The Container Timing state accumulated for one container root, i.e. one element carrying a containertiming attribute.

https://wicg.github.io/container-timing/

Fields

contributing_nodes: FxHashSet<OpaqueNode>

Descendant nodes that have already contributed painted area to this container, at any point in the past. Once a node is in this set it is never reconsidered. TODO: This algorithm could change in future https://github.com/WICG/container-timing/issues/72

painted_region: PaintedRegion

Everything painted inside this container so far, de-overlapped. Only ever grows by merging in a genuinely new node’s region (see contributing_nodes); persists across display list builds.

last_painted_element: Option<OpaqueNode>

The descendant whose paint most recently grew painted_region, for PerformanceContainerTiming::lastPaintedElement.