https://github.com/WebKit/WebKit/pull/4490/
<rdar://problem/100129199>
Committed 254638@main (be59551cc253): <https://commits.webkit.org/254638@main> Reviewed commits have been landed. Closing PR #4490 and removing active labels.
Why?
To improve compilation time: BorderValue.h is included by RenderStyle.h which is itself included by many parts of WebCore.