webkitgtk: 2.10.4 -> 2.10.9

[k0ral]

Motivation for this change

Solve #17308: upgrade webkitgtk 2.10 branch, and set default branch to 2.12 (transparent since no derivation was pointing to webkitgtk)

Things done

• Tested using sandboxing
  (nix.useChroot on NixOS,
  or option build-use-chroot in nix.conf
  on non-NixOS)
• Built on platform(s)
  • NixOS
  • OS X
  • Linux
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested compilation of modified pkg
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

---

Cc @RamKromberg

[mention-bot]

@k0ral, thanks for your PR! By analyzing the annotation information on this pull request, we identified @ryantrinkle, @lethalman and @vcunat to be potential reviewers

[joachifm]

This travis error looks legit: https://travis-ci.org/NixOS/nixpkgs/jobs/149596246. Big 👍 otherwise. Do you have a rough estimate of the amount of rebuilds this is likely to trigger? (Just in case it needs to go to staging first, I mean).

[vcunat]

I don't think this should need to go through staging.

[k0ral]

I've fixed the libobjc issue, now Travis fails because of what looks like a networking error.

[RamKromberg]

Travis fails because of what looks like a networking error.

I'm guessing travis will fail regardless since the build will take too long.

I don't think this should need to go through staging.

I tend to agree seeing how no one can/will compile & test it unless it's available in binary form. Well, it's called unstable for a reason... :D

[joachifm]

@RamKromberg the binaries produced while evaluating staging are still available, so it wouldn't make any difference in that respect, I think. Anyway, given the lack of objections to this, I think we should just go ahead.