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,
+}
+
diff --git a/transport/safe_union/1.0/types.hal b/transport/safe_union/1.0/types.hal
new file mode 100644
index 0000000..bc3dbc2
--- /dev/null
+++ b/transport/safe_union/1.0/types.hal
@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2018 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package android.hidl.safe_union@1.0;
+
+/**
+ * Unit type easily available to be used with safe_union.
+ *
+ * Example usage:
+ *
+ * safe_union MaybeFoo {
+ *     Monostate no_init;
+ *     Foo foo;
+ * };
+ */
+struct Monostate {};
diff --git a/update-makefiles.sh b/update-makefiles.sh
index 1a0b892..cf13c83 100755
--- a/update-makefiles.sh
+++ b/update-makefiles.sh
@@ -7,6 +7,7 @@
     android.hidl.manager@1.1
     android.hidl.manager@1.2
     android.hidl.memory@1.0
+    android.hidl.safe_union@1.0
     android.hidl.token@1.0
 )