turns chunks into compositor layers & updates cc property trees.

 Consumes the new PaintArtifact and does the layerization and property‑tree updates required for compositor draw. It supports fast paths when only values changed (e.g., opacity) or when a scroll only induces raster invalidation, avoiding full rebuilds. It owns a subtree of cc layers corresponding to the artifact. (Chromium Git Repositories)

Key fields

• scoped_refptr root_layer_ — root of the Blink‑owned layer subtree.

• UpdateType needs_update_ — kRepaint vs kFull (or scroll fast path).

• Caches/maps for synthesized mask clips and scroll translations seen while layerizing. (Chromium Git Repositories)

Most important methods

• bool TryFastPathUpdate(const PaintArtifact&) — take a cheap path (no topology change). (Chromium Git Repositories)

• void Update(const PaintArtifact&, const ViewportProperties&, const StackScrollTranslationVector&, Vector>) — full reconciliation to layers + cc property trees. (Chromium Git Repositories)

• “Direct update” helpers like DirectlyUpdateCompositedOpacityValue(...), DirectlyUpdateScrollOffsetTransform(...) — skip rebuilds for common animations/scrolling. (Chromium Git Repositories)

Hands off to: PropertyTreeManager (internally) to mirror Blink property nodes to cc trees, ready for commit to the compositor thread.