Any struct that is defined in core.mojom with the skipHeader tag needs to be present in ipa_interface.h, either forward-declared or #included. Add a comment so that, in the future, people don't try to send patches removing the seemingly unused forward-declaration. Signed-off-by: Paul Elder <paul.elder@ideasonboard.com> Reviewed-by: Niklas Söderlund <niklas.soderlund@ragnatech.se> Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>