26 diagnostic asserts from 25 installs of Firefox 151.0a1.

Crash report: https://crash-stats.mozilla.org/report/index/f4974bfb-5d01-41d3-8a0c-613760260409

MOZ_CRASH Reason:

MOZ_DIAGNOSTIC_ASSERT(XRE_IsParentProcess())

Top 10 frames:

0  xul.dll  mozilla::net::HttpBaseChannel::DoApplyContentConversionsInternal(nsIStreamLis...  netwerk/protocol/http/HttpBaseChannel.cpp:1582
1  xul.dll  mozilla::net::HttpBaseChannel::DoApplyContentConversions(nsIStreamListener*, ...  netwerk/protocol/http/HttpBaseChannel.cpp:1475
1  xul.dll  mozilla::net::HttpChannelChild::DoOnStartRequest(nsIRequest*)  netwerk/protocol/http/HttpChannelChild.cpp:603
2  xul.dll  mozilla::net::HttpChannelChild::OnStartRequest(mozilla::net::nsHttpResponseHe...  netwerk/protocol/http/HttpChannelChild.cpp:522
2  xul.dll  mozilla::net::HttpChannelChild::ProcessOnStartRequest::<lambda_1>::operator()...  netwerk/protocol/http/HttpChannelChild.cpp:363
2  xul.dll  std::invoke(mozilla::net::HttpChannelChild::ProcessOnStartRequest::<lambda_1>&)  /builds/worker/fetches/vs/VC/Tools/MSVC/14.50.35717/include/type_traits:1678
2  xul.dll  std::_Func_impl_no_alloc<`lambda at /builds/worker/checkouts/gecko/netwerk/pr...  /builds/worker/fetches/vs/VC/Tools/MSVC/14.50.35717/include/functional:883
3  xul.dll  mozilla::net::ChannelEventQueue::FlushQueue()  netwerk/ipc/ChannelEventQueue.cpp:81
4  xul.dll  mozilla::net::ChannelEventQueue::MaybeFlushQueue()  netwerk/ipc/ChannelEventQueue.h:348
4  xul.dll  mozilla::net::ChannelEventQueue::CompleteResume()  netwerk/ipc/ChannelEventQueue.h:333

It's very weird we're getting these for sites like about:blank and about:newtab (and one file:/// link)

Early compression dictionary code had a window where cache entries could be
written with dcb or dcz in the Content-Encoding response-head metadata but
with already-decompressed data in the body. When such an entry is later served,
the mismatch causes crashes in content processes (MOZ_DIAGNOSTIC_ASSERT in
DoApplyContentConversionsInternal).

In OnCacheEntryCheck, doom any cache entry whose stored Content-Encoding
contains "dcb" or "dcz" and treat it as ENTRY_NOT_WANTED so the channel falls
through to a normal network fetch.

Track how often OnCacheEntryCheck encounters and dooms stale cache entries
with dcb/dcz Content-Encoding. The counter lets us monitor when the stale-entry
population from early compression dictionary builds has died out, at which
point the purge check and this metric can be removed. Expires at Firefox 140.

Backed out for causing glean related bustages.

Backout link: https://hg.mozilla.org/integration/autoland/rev/08cc049b3bbd

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&revision=b2affaecbfaed16440506863e97ace65dd24b5f1&selectedTaskRun=XuF6C4GQSRSFi9qvlpQj3A.0

Failure logs:
https://treeherder.mozilla.org/logviewer?job_id=567500855&repo=autoland&task=XuF6C4GQSRSFi9qvlpQj3A.0&lineNumber=6078
https://treeherder.mozilla.org/logviewer?job_id=567500795&repo=autoland&task=MP0gXX5_QLuuBtsOKdi0Kg.0&lineNumber=484
https://treeherder.mozilla.org/logviewer?job_id=567500845&repo=autoland&task=D_z_xeIGRUae3NPthpgXDw.0&lineNumber=362

Reverted this because it was causing build bustages in nsHttpChannel.cpp.

• Revert link
• Push with failures
• Failure Log
• Failure line: /builds/worker/checkouts/gecko/netwerk/protocol/http/nsHttpChannel.cpp:X:7: error: no member named 'stale_dcb_dcz_cache_entries_purged' in namespace 'mozilla::glean::http'; did you mean 'glean::http3::stale_dcb_dcz_cache_entries_purged'?

https://hg.mozilla.org/mozilla-central/rev/95e21ace111a
https://hg.mozilla.org/mozilla-central/rev/afa2c07d6e94

Since nightly and release are affected, beta will likely be affected too.
For more information, please visit BugBot documentation.

I'm seeing some crash volume under this signature but most of the machines involved appear to be old so I'd chalk it up to flaky hardware.