Fix "fallthrough annotation in unreachable code" in release d3d builds The same issue I ran into in https://crrev.com/c/6231111 but on d3d Bug: angleproject:394129077 Change-Id: I90faa01fa66c514162a1d5e4cbe56a2bfd85085e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6237859 Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Cody Northrop <cnorthrop@google.com> Auto-Submit: Roman Lavrov <romanl@google.com>