On the worker-thread only the static `write` methods are actually used, and on the main-thread only class instances are being created.
Hence this, after PR 20197, leads to a bunch of dead code in both of the *built* `pdf.mjs` and `pdf.worker.js` files.
This patch reduces the size of the `gulp mozcentral` output by `21 419` bytes, i.e. `21` kilo-bytes, which I believe is way too large of a saving to not do this.
(I can't even remember the last time we managed to reduce build-size this much with a single patch.)
Follow up on https://github.com/mozilla/pdf.js/pull/20197,
This serializes pattern data into an ArrayBuffer which is
then transferred from the worker to the main thread.
It sets up the stage for us to eventually switch to a
SharedArrayBuffer in the future.