Add member typedef referring to base interface

A member typedef named "BaseInterface" is added to BnInterface and
BpInterface to refer to the base interface class.

Test: Builds

Bug: 123736523
Change-Id: Iae4c18cb037481edc357fde1edc718acb79ecc23
diff --git a/libs/binder/include/binder/IInterface.h b/libs/binder/include/binder/IInterface.h
index f6381f7..0d30560 100644
--- a/libs/binder/include/binder/IInterface.h
+++ b/libs/binder/include/binder/IInterface.h
@@ -54,6 +54,7 @@
     virtual const String16&     getInterfaceDescriptor() const;
 
 protected:
+    typedef INTERFACE           BaseInterface;
     virtual IBinder*            onAsBinder();
 };
 
@@ -66,6 +67,7 @@
     explicit                    BpInterface(const sp<IBinder>& remote);
 
 protected:
+    typedef INTERFACE           BaseInterface;
     virtual IBinder*            onAsBinder();
 };