8031695: CHA ignores default methods during analysis leading to incorrect code generation

Reviewed-by: jrose, acorn, hseigel, lfoltan

hotspot/src/share/vm/code/dependencies.cpp

@@ -1223,11 +1223,9 @@ bool Dependencies::is_concrete_method(Method* m) {
 
   // We could also return false if m does not yet appear to be
   // executed, if the VM version supports this distinction also.
+  // Default methods are considered "concrete" as well.
   return !m->is_abstract() &&
-         !InstanceKlass::cast(m->method_holder())->is_interface();
-         // TODO: investigate whether default methods should be
-         // considered as "concrete" in this situation.  For now they
-         // are not.
+         !m->is_overpass(); // error functions aren't concrete
 }