Chrome object URLs are not revoked after New Identity

In legacy/trac#15502 (moved) this problem is completely described, but applied measures don't solve it. The docs say "Browsers will release these automatically when the document is unloaded". So, either document is never unloaded, or Mozilla forgot to implement this. Testcase is also in legacy/trac#15502 (moved) (creates blobs even when JS is disabled). Leftovers are visible in about:memory:

35 (100.0%) -- dom-media-stream-urls
├──22 (62.86%) -- owner unknown
│  ├───1 (02.86%) ── blob:null/25779196-2491-42e5-8f69-4e52ac6ceb65
│  ...
├───8 (22.86%) -- owner(re[/pdf.js/build/pdf.worker.js)](/pdf.js/build/pdf.worker.js))
│   ├──1 (02.86%) ── blob:re[/pdf.js/1ef14a0f-a417-47cb-9955-8b9f18a43e2c](/pdf.js/1ef14a0f-a417-47cb-9955-8b9f18a43e2c)
│   ...
└───1 (02.86%) ── owner(https://people.torproject.org/~mikeperry/transient/tests/blob-uri-creation.html)/blob:https://people.torproject.org/e66522b9-85ea-4743-a773-aab2deb7bdc5