The provided text outlines the Blink rendering engine's multi-year transition away from its legacy PaintLayer tree toward a more efficient RenderingNG architecture. Traditionally, PaintLayers managed stacking contexts and compositing decisions, but these roles are now largely superseded by modern property trees and the Composite After Paint initiative. This shift addresses the "fundamental compositing bug" by decoupling layers from specific DOM elements, allowing for superior handling of layout fragments and visual correctness. While the PaintLayer class still handles certain tasks like scroll coordination and sticky positioning, it is now considered a deprecated implementation detail slated for full removal. Ultimately, the goal is to streamline the rendering pipeline into a high-performance system driven by global display lists and fragment-based structures.