CSSParserContext stores a handle to a UseCounter directly instead of deriving it from the Document, so it's difficult for consumers to easily switch UseCounter to Deprecation.
I'm going to refactor CSSParserContext to have a handle to a Document instead to fix this. This should also make it possible to clean up CSSValue::consumeGeneratedImage.
Comment 1 by kochi@chromium.org
, Nov 24 2016