For some platforms that can't resize, it's not expected that setWindowFrame has any effect. However, it and other completion handler-based methods need to always call the completion handler. For example, some of those methods are called when going in/out of fullscreen.
<rdar://problem/47981961>
Created attachment 361723 [details] Patch
Comment on attachment 361723 [details] Patch r=me
Comment on attachment 361723 [details] Patch Clearing flags on attachment: 361723 Committed r241285: <https://trac.webkit.org/changeset/241285>
All reviewed patches have been landed. Closing bug.