We have a bunch of stuff in LayersLogging.* that knows how to stringify various types and structs for debug-printing. It's a bit inconsistent though and having this code centralized in LayersLogging.* rather than embedded in the individual classes/structs seems odd.

I would like to make it so that each struct that we care about logging has a built-in function that can serialize itself to an ostream. This seems like a quasi-standard way of doing things, in that the gtest framework will look for such a mechanism to print structures on failed assertions.

The gfx/2d code already has this in some places so I'm just proposing we use that consistently everywhere instead of having to pick one of the many places we have to generate logging.

As a bonus it would be nice to fix https://bugzilla.mozilla.org/show_bug.cgi?id=1334042 so MOZ_LOG can then take these structs directly in a streaming style.

Note that we have a ToString() function which uses operator<<, similar to the way Stringify uses the LayersLogging AppendToString functions. As part of this cleanup, we may want to unify the two.

Indeed. We should dump Stringify after this unification.

https://treeherder.mozilla.org/#/jobs?repo=try&group_state=expanded&selectedTaskRun=LsNwHFNHQoS7UN1EPVx6hw.0&revision=e0fc6c7f91a1faa5e268cf7d1588a6c50e4a556a

This also adds all the missing flags to the serializer.

Depends on D93142

This also adds some missing types to the serializer.

Depends on D93143

Depends on D93144

The remaining functions are moved to be with their brethren in xpcom.

Depends on D93145

https://hg.mozilla.org/mozilla-central/rev/1a3828a49bce
https://hg.mozilla.org/mozilla-central/rev/8722892ad618
https://hg.mozilla.org/mozilla-central/rev/ba47f161259a
https://hg.mozilla.org/mozilla-central/rev/5f57cee9e5d3
https://hg.mozilla.org/mozilla-central/rev/aa3bbbc5a7d3