HTMLImageElement.prototype.src Setter

This is a sophisticated programming technique used by Speed Kit's algorithm to accurately measure the Largest Contentful Paint (LCP) on complex, JavaScript-heavy sites. It allows Speed Kit to intercept and know the exact moment a script assigns a source URL to an image tag. This is crucial for identifying the true LCP element and its load time when the main image is loaded dynamically by JavaScript rather than being present in the initial HTML.