Today, the code in media controls explicitly sets inline styles on specific controls to hide or show them. This can be completely eliminated if we instead manipulate state using DOM attributes. For example, if a network error occurs, we can set "disabled" attribute on the timeline control, and then specify in mediaControls.css: video::-webkit-media-controls-timeline:disabled { display: none; } Unfortunately, this is not immediately possible due to a restriction on how CSS selectors can be combined: the pseudo-element selector must always be the last one. Otherwise, the selector is deemed invalid. Hyatt suggested that we relax this requirement, much the same way we relaxed it to allow scrollbar styling.