Support custom flattenable types for RPC.
diff --git a/tools/aidl/aidl_language.h b/tools/aidl/aidl_language.h
index 985f646..b490a59 100644
--- a/tools/aidl/aidl_language.h
+++ b/tools/aidl/aidl_language.h
@@ -64,6 +64,7 @@
 
 enum {
     PARCELABLE_TYPE = 12,
+    FLATTENABLE_TYPE,
     INTERFACE_TYPE_BINDER,
     INTERFACE_TYPE_RPC
 };