Created attachment 103846 [details]
I suspect that the Windows builds failure is due to WebKit.idl not being touched by the patch.
Comment on attachment 103846 [details]
I do wonder if there should be a way for web authors to opt in to this behavior in the browser.
Windows build fix in r93015.
Defaults key renamed in r93027.
As Simon alluded to, there should be a way to opt in to this behavior: Bug 114304