Fixed isVisibleToUserForAutofill() so it returns true by default.

This new API was introduced during the compat app changes and it must be
implemented by views providing virtual views (like WebView). If they don't, we
need to keep the default behavior of assuming the child is visible, otherwise
we might trigger Save when the child value change and the service sets the
FLAG_SAVE_ON_ALL_VIEWS_INVISIBLE

Test: atest CtsAutoFillServiceTestCases:VirtualContainerActivityTest#testSaveNotShownWhenVirtualViewValueChanges

Fixes: 73172668

Change-Id: I80654aaffa7dd24a3b3b59e7016bd86b48fe4898