libbinder: mark transact as final

Subclasses of BpBinder/BBinder should override onTransact, not transact.

Bug: 136027762
Test: TH
Change-Id: I1d48ac8c4b5cb147e1d378e6ce1238338d93d3e7
diff --git a/libs/binder/include/binder/Binder.h b/libs/binder/include/binder/Binder.h
index 1537e69..dec75f5 100644
--- a/libs/binder/include/binder/Binder.h
+++ b/libs/binder/include/binder/Binder.h
@@ -38,7 +38,7 @@
     virtual status_t    transact(   uint32_t code,
                                     const Parcel& data,
                                     Parcel* reply,
-                                    uint32_t flags = 0);
+                                    uint32_t flags = 0) final;
 
     // NOLINTNEXTLINE(google-default-arguments)
     virtual status_t    linkToDeath(const sp<DeathRecipient>& recipient,
diff --git a/libs/binder/include/binder/BpBinder.h b/libs/binder/include/binder/BpBinder.h
index e71541b..28599f4 100644
--- a/libs/binder/include/binder/BpBinder.h
+++ b/libs/binder/include/binder/BpBinder.h
@@ -45,7 +45,7 @@
     virtual status_t    transact(   uint32_t code,
                                     const Parcel& data,
                                     Parcel* reply,
-                                    uint32_t flags = 0);
+                                    uint32_t flags = 0) final;
 
     // NOLINTNEXTLINE(google-default-arguments)
     virtual status_t    linkToDeath(const sp<DeathRecipient>& recipient,