+++ This bug was initially created as a clone of Bug #1374847 +++ nsIPrefBranch2 and nsIPrefBranchInternal are both trivial subclasses of nsIPrefBranch which exist purely for add-on compatibility.
Created attachment 8894804 [details] [diff] [review] 1388275-pref2.patch Version upgrades to current supported levels (which I think should not go beyond Fx 56). Tested with older SeaMonkey and TB versions too.
Comment on attachment 8894804 [details] [diff] [review] 1388275-pref2.patch LGTM r=me
I thought I needed to set the minimum Gecko versions too but doesn't look this way. https://hg.mozilla.org/dom-inspector/rev/fd6400256ecdb7df0ff66675e51a6dec9088478f https://hg.mozilla.org/dom-inspector/rev/9b13e3ad66cf993b30ba6e40e144a7d6428f43c0