Currently we're loading the `web/annotation_layer_builder.css` and `web/xfa_layer_builder.css` files *directly* during the reference tests.
This becomes a problem is we want to reduce duplication in the CSS-files, e.g. by placing *common* rules in the `web/pdf_viewer.css` file.
Given that `gulp components` is already being utilized when running tests, we can thus use that to instead depend on the *entire* viewer-components CSS-file in the reference tests.