Interface for hidl forward reference test

Test proofs that forward reference can now be used.
Test contains trie implementation and some forward reference examples.

Bug: 31827278

Test: hidl_test

Change-Id: I55cdde500baea3e70ebf4466c681ad652b6ff9fd
diff --git a/tests/trie/1.0/ITrie.hal b/tests/trie/1.0/ITrie.hal
new file mode 100644
index 0000000..5d009ca
--- /dev/null
+++ b/tests/trie/1.0/ITrie.hal
@@ -0,0 +1,23 @@
+/*
+ * Copyright (C) 2017 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.hardware.tests.trie@1.0;
+
+interface ITrie {
+    newTrie() generates (TrieNode trie);
+    addStrings(TrieNode trie, vec<string> strings) generates (TrieNode trie);
+    containsStrings(TrieNode trie, vec<string> strings) generates (vec<bool> contains);
+};