Fix Dialog default callback registering at the wrong priority.

Bug:259602785
Test: In a standalone app, register a callback in Dialog#onCreate() with default priority. Make sure the dialog callback can be invoked.
Test: BackNavigationTests#registerCallback_dialog (run on master)

Change-Id: I9cfd596611fb341389cda44e3605c1e99ddc3791

core/java/android/app/Dialog.java

@@ -458,8 +458,7 @@ public class Dialog implements DialogInterface, Window.Callback,
                 && WindowOnBackInvokedDispatcher.isOnBackInvokedCallbackEnabled(mContext)) {
             // Add onBackPressed as default back behavior.
             mDefaultBackCallback = this::onBackPressed;
-            getOnBackInvokedDispatcher().registerOnBackInvokedCallback(
-                    OnBackInvokedDispatcher.PRIORITY_DEFAULT, mDefaultBackCallback);
+            getOnBackInvokedDispatcher().registerSystemOnBackInvokedCallback(mDefaultBackCallback);
             mDefaultBackCallback = null;
         }
     }