file-menu:open-callback in drscheme:frame:basics-mixin

This method is called when the open menu-item of the file-menu menu is selected.

• (send a-drscheme:frame:basics-mixin file-menu:open-callback item evt void
     item : (instance (derived-from menu-item%))
     evt : (instance control-event%)

  Calls handler:edit-file.