Correct / real URLs should be enforced, to avoid breaking adblockers

Currently there is no enforced relationship between the URL used to look up resources in the package, and where the resource came from online. Consistent URLs are an imperfect, but extremely useful signal for privacy protecting tools (filter lists, adblockers, disconnect, Firefox and Edge built in protections, safe browsing, etc.).

The current proposal would allow for all WebPackage'd sites to circumvent all URL based tools by simply randomizing URLs as a post processing step in amppackager or similar. This could even be done per-request per page. Since URLs are effectively just indexes into the package (and not keys for decision making, caching, etc), they can be changed arbitrarily w/o affecting how the package loads, but preventing the URL-based privacy preserving tools from running.

A (partial) possible solution to the problem is to play a cut-and-choose, commitment-auditing style games with the URLs. At package time, the packager has to make commitments about which URL each resource came from, and the size, shape etc of the resource. These can be made / mixed with the URL of the page being packaged.

The client can then, w/ some probability, audit some number of the URLs in the package. If the commitments fail, deterring counter measures can be taken against the packing origin (e.g. global decaying block list of misbehaving packagers, etc).

Start by reading the issue proposal and its 43-comment discussion, then inspect the referenced amppackager project and the cut-and-choose commitment-auditing paper. No files or tests are named; done would require an agreed, enforceable design for preserving and auditing resource URL provenance without letting packagers randomize URLs.