The provided document details Blink's StyleEngine, a crucial component within Chromium's rendering engine responsible for managing all CSS styles for a web document. It orchestrates style data and operations, maintaining stylesheets, rule sets, and caches for efficient style calculations. The StyleEngine employs a lazy invalidation strategy to optimize performance, avoiding immediate recalculations on every DOM change by using flags and invalidation sets to mark elements that require restyling later. This two-phase process of invalidation and recalculation ensures that styles are updated only when necessary, minimizing computational overhead. Furthermore, the StyleEngine integrates deeply with other subsystems like the StyleInvalidator, StyleResolver, and interacts with DOM updates, CSSOM, media queries, and even the layout and painting phases of rendering, continually evolving to support new CSS features and optimize performance.