ComputedStyleExtractor has always been contained in CSSComputedStyleDeclaration.h but it's a public class and deserves to be in its own source file.
Pull request: https://github.com/WebKit/WebKit/pull/4534
Committed 254712@main (0e80c5909d7e): <https://commits.webkit.org/254712@main> Reviewed commits have been landed. Closing PR #4534 and removing active labels.
<rdar://problem/100208238>