Bumping gaia.json for 6 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/c09f78f6bdd9
Author: Gareth Aye <gaye@mozilla.com>
Desc: Merge pull request #12992 from gaye/bug-920261

Bug 920261 - mailto links broken r=jrburke

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https://hg.mozilla.org/integration/gaia-central/rev/5daf75353a52
Author: Gareth Aye <gaye@mozilla.com>
Desc: Bug 920261 - fix mailto links r=jrburke

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https://hg.mozilla.org/integration/gaia-central/rev/57e87158185f
Author: George <georgeiscoming@gmail.com>
Desc: Merge pull request #13002 from cctuan/926871

Bug 926871 - Prevent reflowing when the software button is hidden and add test cases for software button manager

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https://hg.mozilla.org/integration/gaia-central/rev/3b52ff85884c
Author: cctuan <georgeiscoming@gmail.com>
Desc: Bug 926871 - Prevent reflowing when the software button is hidden

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https://hg.mozilla.org/integration/gaia-central/rev/45d9ade0030c
Author: Diego Marcos <diego.marcos@gmail.com>
Desc: Merge pull request #13097 from dmarcos/bug928614

Bug 931054 - [Camera] filmstrip.js access undefined preview metadata

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https://hg.mozilla.org/integration/gaia-central/rev/412e5f78f422
Author: Diego Marcos <diego.marcos@gmail.com>
Desc: Bug 931054 - [Camera] filmstrip.js access undefined preview metadata