As was mentioned in https://bugzilla.mozilla.org/show_bug.cgi?id=1626570#c118, there were some performance regressions in connection with the introduction of CopyableAutoTArray, in particular with WebAudio.

This is likely to be caused by missed optimization / copy elision opportunities due to the calling of the base class' Clone method which returns an AutoTArray instead of a CopyableAutoTArray. Changing this to an ordinary copy reverts the performance regression as can be observed here:

https://treeherder.mozilla.org/perf.html#/comparesubtest?originalProject=mozilla-central&newProject=try&newRevision=85724fd24502163650b7e5e4378d15d52baa3b88&originalSignature=1931866&newSignature=1904634&framework=10&selectedTimeRange=172800

CopyableAutoTArray should be deleted to avoid doing this accidentally as in this case.

Bugbug thinks this bug is a defect, but please change it back in case of error.

Set release status flags based on info from the regressing bug 1626570

I am not sure if this should be regarded a defect. It does not fix a functional issue, but reverts a performance regression, which I am not sure is significant enough to be regarded a defect.

Nice find, thanks for looking into this!

https://hg.mozilla.org/mozilla-central/rev/53776f985a81