Bug 1864488 - Avoid reply message types in IPC fuzzing. r=truber

Differential Revision: https://phabricator.services.mozilla.com/D193451

tools/fuzzing/ipc/IPCFuzzController.cpp

@@ -142,6 +142,11 @@ bool IPCFuzzController::GetRandomIPCMessageType(ProtocolId pId,
 
   *type =
       ((uint32_t)pIdEntry->first << 16) + 1 + (typeOffset % pIdEntry->second);
+
+  if (strstr(IPC::StringFromIPCMessageType(*type), "::Reply_")) {
+    *type = *type - 1;
+  }
+
   return true;
 }