Note that &closeTab.label; which is used in this file is also available from browser.dtd.

I can confirm this fixes the problem for the single process nightly branch.

I tried your fixed version and it works fine except that the "open link in new tab" gesture doesn't work.

Does this perhaps require tabbrowser.dtd?

@mpopp75 That gesture works for me. When you edited the extension did you increment the version number and remove the meta directory?

I did this: got a clone of https://github.com/ehsan/firegestures.git, switched to branch 99, incremented the version number in install.rdf to 1.11a1 and created a zip file which I renamed to firegestures.xpi. This I installed. I don't see any meta (or META-INF) directory.

I used my default Firefox profile to test it which has a number of other addons installed. I can't rule out that some other addon breaks this newly fixed version, but it definitely worked with the same addons before Firegestures broke in Nightly.

I don't really understand how removing tabbrowser.dtd could have changed anything with regards to opening a link in a new tab, sorry. This extension doesn't reference that file any more, so I don't think that is related to this issue.

Interestingly, with Firefox 40.0 (probably earlier versions too) the open a link in a new tab gesture works fine.

As of today's Nightly, unverified addons no longer work. Since this fixed version definitely solves the majority of problems and doesn't seem to break anything that wasn't broken (i.e. the addon being broken with e10s which this is all about), I would recommend releasing this fixed version (also to get it verified by Mozilla). If any problems remain, it's easier to tackle them from there.

@mpopp75 In about:config change "xpinstall.signatures.required" to false. The meta-inf is only in the official 1.10 download on the Mozilla addons site. You should download that and modify it.

Even with "xpinstall.signatures.required" set to false I can't install the updated version, at least for now. Since the verification stuff in Firefox is very new, maybe there are still some flaws which need fixing.

"xpinstall.signatures.required" works now and I tried the modified addon with default settings in a fresh & up-to-date Nightly profile. However the "open link in a new tab" gesture still doesn't work.

But I noticed a message saying: Starting point of gesture is not on a link. Even though it certainly was. Maybe there is some other issue with that.

It could also have to do with me using the Linux64 version of Firefox (Xubuntu 15.04, 64bit), in case there is some platform dependent problem.

Thanks, ehsan.
I have merged your pull request.