I tried to do this in bug 1696158, but it's complicated so we decided to split it off into a separate bug. The field is currently stored on the nsDocLoader but should probably move to the Document.

Rolling over the remaining Fission M7a bugs to the Fission M8 milestone.

Backed out for failures on iframe-cross-origin-print.sub.html

• backout: https://hg.mozilla.org/integration/autoland/rev/d7f8d3c47d9556562be8c9510e6bcf4b6224f015

• push: https://treeherder.mozilla.org/jobs?repo=autoland&selectedTaskRun=ALBUrYH7SKe1VIj8gCSoGQ.0&revision=b6399ca8a2c185e00b3928af0b6e639495a11823&group_state=expanded

• failure log: https://treeherder.mozilla.org/logviewer?job_id=345677545&repo=autoland&lineNumber=5165

[task 2021-07-19T21:34:56.927Z] 21:34:56     INFO - PID 4174 | ### XPCOM_MEM_BLOAT_LOG defined -- logging bloat/leaks to /tmp/tmpsrnwckbb/runtests_leaks_1149_tab_pid4758.log
[task 2021-07-19T21:34:56.928Z] 21:34:56     INFO - PID 4174 | [4758, Main Thread] WARNING: XPCOM_MEM_BLOAT_LOG is set, disabling native allocations.: file /builds/worker/checkouts/gecko/tools/profiler/core/platform.cpp:248
[task 2021-07-19T21:34:56.956Z] 21:34:56     INFO - PID 4174 | [Child 4758, Main Thread] WARNING: could not set real-time limit in CubebUtils::InitLibrary: file /builds/worker/checkouts/gecko/dom/media/CubebUtils.cpp:619
[task 2021-07-19T21:35:23.630Z] 21:35:23     INFO - PID 4174 | [Parent 4174, Compositor] WARNING: Possibly dropping task posted to updater thread: file /builds/worker/checkouts/gecko/gfx/layers/apz/src/APZUpdater.cpp:370
[task 2021-07-19T21:35:23.666Z] 21:35:23     INFO - PID 4174 | [Child 4420, Main Thread] WARNING: NS_ENSURE_SUCCESS(GetWindowDimensions(dimensions), NS_ERROR_FAILURE) failed with result 0x80004005 (NS_ERROR_FAILURE): file /builds/worker/checkouts/gecko/dom/base/nsFrameLoader.cpp:2456
[task 2021-07-19T21:35:23.687Z] 21:35:23     INFO - PID 4174 | [Child 4420, Main Thread] WARNING: IPC message discarded: actor cannot send: file /builds/worker/checkouts/gecko/ipc/glue/ProtocolUtils.cpp:527
[task 2021-07-19T21:35:23.687Z] 21:35:23     INFO - PID 4174 | [Child 4420, Main Thread] WARNING: Attempt to __delete__ missing or closed actor: file /builds/worker/workspace/obj-build/ipc/ipdl/PBrowserBridgeChild.cpp:59
[task 2021-07-19T21:35:23.687Z] 21:35:23     INFO - PID 4174 | [Child 4420, Main Thread] ###!!! ASSERTION: User did not call nsIContentViewer::Destroy: '!mPresShell && !mPresContext', file /builds/worker/checkouts/gecko/layout/base/nsDocumentViewer.cpp:567
[task 2021-07-19T21:35:23.736Z] 21:35:23  WARNING - Failed to get assertion count; window was closed
[task 2021-07-19T21:35:23.769Z] 21:35:23  WARNING - Failed to get assertion count; window was closed
[task 2021-07-19T21:35:23.772Z] 21:35:23     INFO - TEST-UNEXPECTED-TIMEOUT | /html/browsers/windows/iframe-cross-origin-print.sub.html | expected PASS
[task 2021-07-19T21:35:23.772Z] 21:35:23     INFO - TEST-INFO took 30175ms

Also failing test-verify : TEST-UNEXPECTED-FAIL | docshell/test/navigation/test_blockBFCache.html | Test timed out. -

This bug is a hard blocker for Fission M8.

When we're static cloning a remote document for printing we're calling OOPChildLoadStarted, but we never call OOPChildLoadDone. That used to not a be a problem. Now that we're adding the document onload blocker to the loadgroup from OOPChildLoadStarted, that causes us to not print, because we check if the load group is empty before starting to print.
I have a patch that's looking promising on try.

Setting status-firefox92=wontfix because we don't need to uplift this fix to Beta 92.

https://hg.mozilla.org/mozilla-central/rev/f912045db98d

Backed out for causing content crashes (bug 1725558):
https://hg.mozilla.org/mozilla-central/rev/7ed9cc05197163c00d174e94caa221ebbf41c718

(In reply to Sebastian Hengst [:aryx] (needinfo on intermittent or backout) from comment #11)

Backed out for causing content crashes (bug 1725558):
https://hg.mozilla.org/mozilla-central/rev/7ed9cc05197163c00d174e94caa221ebbf41c718

Apparently that didn't resolve the crashes, and suspicion is on bug 1710879. Relanding.

https://hg.mozilla.org/mozilla-central/rev/448496ef188d