Since the default value for the second part of scroll-snap-type is "proximity" it should serialize to an empty string. This will fix a couple scroll snapping tests from the WPT suite.
Created attachment 410925 [details]
Created attachment 410930 [details]
Comment on attachment 410930 [details]
Still one test failure.
Created attachment 411101 [details]
Committed r268348: <https://trac.webkit.org/changeset/268348>
All reviewed patches have been landed. Closing bug and clearing flags on attachment 411101 [details].