Bug 1447480 - Add support of MOZ_FALLTHROUGH_ASSERT without any argument r=hsivonen

MozReview-Commit-ID: 6xrdrggcVFR

--HG--
extra : rebase_source : 0f3b30d0e48e402bbc6365dcb25146dffeb8ad97

mfbt/Assertions.h

@@ -596,6 +596,7 @@ struct AssertionConditionType
  * }
  */
 #ifdef DEBUG
+#  define MOZ_FALLTHROUGH_ASSERT() MOZ_CRASH()
 #  define MOZ_FALLTHROUGH_ASSERT(reason) MOZ_CRASH("MOZ_FALLTHROUGH_ASSERT: " reason)
 #else
 #  define MOZ_FALLTHROUGH_ASSERT(...) MOZ_FALLTHROUGH