Previously, calling `setProperty` or `removeProperty` from JS on a CSSStyleDeclaration returned from `getComputedStyle()` would return null. We now return a NoModificationAllowedError instead, which aligns our implementation with the specification.
CSSStyleSheet.addRule()
remove_rule()
CSSStyleSheet.replace()
CSSStyleSheet.replaceSync()
Element::auto_directionality()
all: revert