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

========

https://hg.mozilla.org/integration/gaia-central/rev/77c4bd80708c
Author: Zac <zcampbell@mozilla.com>
Desc: Merge pull request #14215 from viorelaioia/bug_942107

Bug 942107 - Messages app, Reduce locators

========

https://hg.mozilla.org/integration/gaia-central/rev/b642029ee9a9
Author: Viorela Ioia <viorelaioia@gmail.com>
Desc: Bug 942107 - Messages app, Reduce locators

========

https://hg.mozilla.org/integration/gaia-central/rev/2ff0cbe62c60
Author: gasolin <gasolin@gmail.com>
Desc: Merge pull request #14208 from gasolin/issue-944584

Bug 944584 - Add capture permission to SYSTEM app to enable BOOKMARKED w..., r=alive

========

https://hg.mozilla.org/integration/gaia-central/rev/50fb92f487f6
Author: gasolin <gasolin@gmail.com>
Desc: Bug 944584 - Add capture permission to SYSTEM app to enable BOOKMARKED web pages acquires gUM