Bumping gaia.json for 4 gaia-central revision(s)

========

https://hg.mozilla.org/integration/gaia-central/rev/9486207b6a2e
Author: Jonathan Griffin <jgriffin@mozilla.com>
Desc: Merge pull request #11929 from jonallengriffin/unitdir

Bug 911395 - Only run tests in 'unit' directories, r=Rik, a=test-only

========

https://hg.mozilla.org/integration/gaia-central/rev/776f07313f92
Author: Jonathan Griffin <jgriffin@mozilla.com>
Desc: Bug 911395 - Only run tests in 'unit' directories, r=Rik, a=test-only

========

https://hg.mozilla.org/integration/gaia-central/rev/6bc8c4774c6d
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Merge pull request #9403 from pivanov/bug-798696

Bug 798696 - When viewing single image in Gallery, extremely hard to find button to go back to thumbnail view

========

https://hg.mozilla.org/integration/gaia-central/rev/bd17634f54b0
Author: Pavel Ivanov <pivanov@mozilla.com>
Desc: Bug 798696 - When viewing single image in Gallery, extremely hard to find button to go back to thumbnail view