cast functions for interfaces.

Test: hidl_test

Bug: 32001926

Change-Id: Ia788d775a668c4232c8a017a6b9430ddf16faca3
diff --git a/Interface.cpp b/Interface.cpp
index 09959ae..1d0f37a 100644
--- a/Interface.cpp
+++ b/Interface.cpp
@@ -131,6 +131,10 @@
     return v;
 }
 
+std::vector<const Interface *> Interface::superTypeChain() const {
+    return superType()->typeChain(); // should work even if superType is nullptr
+}
+
 bool Interface::isInterface() const {
     return true;
 }