In Bug 247074 we moved the Masonry feature flag from preview to stable. While the Cocoa build of WebKit needs the feature to be on by default at the moment, we do not need to toggle the feature for other ports. This patch leaves the Cocoa port enabled, but restores the flag to `preview`, and switches the default for non-Cocoa ports back off.
<rdar://problem/123465041>
https://github.com/WebKit/WebKit/pull/24972
Committed 275249@main (c9a9269b077f): <https://commits.webkit.org/275249@main> Reviewed commits have been landed. Closing PR #24972 and removing active labels.