What's the name of this DLL? I assume it's separate from the monster chrome.dll, and that the model is proprietary.

chrome_screen_ai.dll is the name of the dll (libchromescreenai.so on linux) and yes it is proprietary. It isn't included by default, Chrome uses its component service to download it automatically when you open a PDF file that doesn't have pre-existing OCR'd text on it. You can download it separately from here: https://chrome-infra-packages.appspot.com/p/chromium/third_p...