Add safe_union@1.0::Monostate.

This is a helper type used to easily make optional types.

Bug: 116156870
Test: hidl_test, hidl_test_java
Change-Id: If38827800edf362676a99619c3d75114ab8eef13
diff --git a/transport/safe_union/1.0/Android.bp b/transport/safe_union/1.0/Android.bp
new file mode 100644
index 0000000..0fc2305
--- /dev/null
+++ b/transport/safe_union/1.0/Android.bp
@@ -0,0 +1,17 @@
+// This file is autogenerated by hidl-gen -Landroidbp.
+
+hidl_interface {
+    name: "android.hidl.safe_union@1.0",
+    root: "android.hidl",
+    vndk: {
+        enabled: true,
+    },
+    srcs: [
+        "types.hal",
+    ],
+    types: [
+        "Monostate",
+    ],
+    gen_java: true,
+}
+