Maybe Fission related. (DOMFissionEnabled=1)

Crash report: https://crash-stats.mozilla.org/report/index/848482c4-ae1a-460d-b6ea-176370220115

MOZ_CRASH Reason: ```assertion failed: (left == right)
left: `2`,
right: `1````

Top 10 frames of crashing thread:

0 libxul.so RustMozCrash mozglue/static/rust/wrappers.cpp:18
1 libxul.so mozglue_static::panic_hook mozglue/static/rust/lib.rs:91
2 libxul.so core::ops::function::Fn::call library/core/src/ops/function.rs:70
3 libxul.so std::panicking::rust_panic_with_hook library/std/src/panicking.rs:610
4 libxul.so std::panicking::begin_panic_handler::{{closure}} library/std/src/panicking.rs:502
5 libxul.so std::sys_common::backtrace::__rust_end_short_backtrace library/std/src/sys_common/backtrace.rs:139
6 libxul.so rust_begin_unwind library/std/src/panicking.rs:498
7 libxul.so core::panicking::panic_fmt library/core/src/panicking.rs:107
8 libxul.so core::panicking::assert_failed_inner library/core/src/panicking.rs:188
9 libxul.so core::panicking::assert_failed library/core/src/panicking.rs:145

Set release status flags based on info from the regressing bug 1726279

27 reports of this on crash-stats so far, so quite a common issue. I haven't reproduced it locally yet, but I think I know how to solve this anyway.

Bug 1750810 will revert this change for Linux in Nightly 98 until the existing issues are resolved.

The fixes in bug 1757473 should address this crash.

Fixed by bug 1757473.