Add interfaceDescriptor() method to all interfaces

which returns interfaceChain[0].

Bug: 34136228
Test: hidl_test
Test: hidl_test_java
Change-Id: Id0d8139d51f39b1c317d966b305e883e561241b8
diff --git a/Interface.h b/Interface.h
index 87a50bc..5cba6c4 100644
--- a/Interface.h
+++ b/Interface.h
@@ -114,6 +114,7 @@
     std::vector<Method *> mReservedMethods;
     mutable bool mIsJavaCompatibleInProgress;
     Method *createDescriptorChainMethod() const;
+    Method *createGetDescriptorMethod() const;
     Method *createSyspropsChangedMethod() const;
     Method *createLinkToDeathMethod() const;
     Method *createUnlinkToDeathMethod() const;