The initial design for this is to map Vendor ID/Product ID pairs to a landing page and list of allowed origins, the same data that would be available if the device could provide WebUSB Descriptors.

This is blocked on:

1) Determining the format and method for shipping this data with Chrome.
2) Determining a method to validate that submissions are from the owner of the Vendor ID in question.

As of r442105 (released to dev-channel in Chrome 57.0.2977.0) top-level frames may connect to any USB device, regardless of the WebUSB allowed origin descriptors. The descriptors are still checked for requests from iframes.

Given this change I am abandoning the effort to develop a "Public Device Registry" mechanism for the time being.