Bug 1681987 - Add missing includes to fix build with --disable-accessibility. r=andi

Differential Revision: https://phabricator.services.mozilla.com/D99658

dom/plugins/ipc/FunctionBrokerIPCUtils.h

@@ -8,6 +8,7 @@
 #define dom_plugins_ipc_functionbrokeripcutils_h 1
 
 #include "ipc/EnumSerializer.h"
+#include "ipc/IPCMessageUtilsSpecializations.h"
 #include "PluginMessageUtils.h"
 
 #if defined(XP_WIN)