Chromium Compositor Implementation of CSS Sticky Positioning

In Chromium, sticky positioning is managed by the compositor thread to ensure smooth scrolling without relying on the main layout engine. The process begins on the main thread, where layout constraints are calculated and passed to the compositor's property trees, specifically the TransformTree and ScrollTree. By promoting sticky elements to their own composited layers, the engine can adjust their local transforms in real-time based on the current scroll offset. This specialized logic handles complex scenarios such as nested sticky elements, containing block boundaries, and adjustments for mobile browser UI changes. Ultimately, this architecture maintains high performance and seamless hit-testing by avoiding expensive re-layouts during user interaction.