This was originally added in order to centralize the ifdefs, in cl/164484905. However, cl/337142938 undid this aspect of the change, because it broke on Android. What is left is vestigial: `Throw()` can be deleted at no loss, with a warning that should discourage us from ever reintroducing it.

PiperOrigin-RevId: 513391041
Change-Id: I1608a2007eb26ee95df07f3b4b1672c034743832