/usr/include/gcr-3/ is in libgcr-3-dev 3.18.0-1ubuntu1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/gcr-3/gcr/
/usr/include/gcr-3/gcr/gcr-base.h
/usr/include/gcr-3/gcr/gcr-certificate-chain.h
/usr/include/gcr-3/gcr/gcr-certificate-request.h
/usr/include/gcr-3/gcr/gcr-certificate.h
/usr/include/gcr-3/gcr/gcr-collection.h
/usr/include/gcr-3/gcr/gcr-column.h
/usr/include/gcr-3/gcr/gcr-comparable.h
/usr/include/gcr-3/gcr/gcr-deprecated-base.h
/usr/include/gcr-3/gcr/gcr-enum-types-base.h
/usr/include/gcr-3/gcr/gcr-filter-collection.h
/usr/include/gcr-3/gcr/gcr-fingerprint.h
/usr/include/gcr-3/gcr/gcr-icons.h
/usr/include/gcr-3/gcr/gcr-import-interaction.h
/usr/include/gcr-3/gcr/gcr-importer.h
/usr/include/gcr-3/gcr/gcr-library.h
/usr/include/gcr-3/gcr/gcr-mock-prompter.h
/usr/include/gcr-3/gcr/gcr-parser.h
/usr/include/gcr-3/gcr/gcr-pkcs11-certificate.h
/usr/include/gcr-3/gcr/gcr-prompt.h
/usr/include/gcr-3/gcr/gcr-secret-exchange.h
/usr/include/gcr-3/gcr/gcr-secure-memory.h
/usr/include/gcr-3/gcr/gcr-simple-certificate.h
/usr/include/gcr-3/gcr/gcr-simple-collection.h
/usr/include/gcr-3/gcr/gcr-system-prompt.h
/usr/include/gcr-3/gcr/gcr-system-prompter.h
/usr/include/gcr-3/gcr/gcr-trust.h
/usr/include/gcr-3/gcr/gcr-types.h
/usr/include/gcr-3/gcr/gcr-union-collection.h
/usr/include/gcr-3/gcr/gcr-unlock-options.h
/usr/include/gcr-3/gcr/gcr-version.h
/usr/include/gcr-3/gcr/gcr.h
/usr/include/gcr-3/ui/
/usr/include/gcr-3/ui/gcr-certificate-basics-widget.h
/usr/include/gcr-3/ui/gcr-certificate-details-widget.h
/usr/include/gcr-3/ui/gcr-certificate-renderer.h
/usr/include/gcr-3/ui/gcr-certificate-widget.h
/usr/include/gcr-3/ui/gcr-collection-model.h
/usr/include/gcr-3/ui/gcr-combo-selector.h
/usr/include/gcr-3/ui/gcr-deprecated.h
/usr/include/gcr-3/ui/gcr-enum-types.h
/usr/include/gcr-3/ui/gcr-failure-renderer.h
/usr/include/gcr-3/ui/gcr-import-button.h
/usr/include/gcr-3/ui/gcr-key-renderer.h
/usr/include/gcr-3/ui/gcr-key-widget.h
/usr/include/gcr-3/ui/gcr-list-selector.h
/usr/include/gcr-3/ui/gcr-prompt-dialog.h
/usr/include/gcr-3/ui/gcr-renderer.h
/usr/include/gcr-3/ui/gcr-secure-entry-buffer.h
/usr/include/gcr-3/ui/gcr-tree-selector.h
/usr/include/gcr-3/ui/gcr-ui.h
/usr/include/gcr-3/ui/gcr-unlock-options-widget.h
/usr/include/gcr-3/ui/gcr-viewer-widget.h
/usr/include/gcr-3/ui/gcr-viewer.h