CSS: Smart <style> tag updates

[lefetmeofefet]

Currently when style tag content is updated, the whole css inside is recalculated, that's bad for performance.
Instead, it's possible to change the style object directory: styleTag.sheet.cssRules[0].style.color="red".
Use cases to cover:

• property value (green)
• property name (color)
• whole css line (color: green;)
• whole css selector content (color: green; font-size: 24px;)
• css selector (.things>#ikaramba)
• whole css rule (selector + content)
• multiple css rules