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

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https://hg.mozilla.org/integration/gaia-central/rev/877d5f736a7c
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #12072 from alivedise/bugzilla/914564/listmenu-clean

Bug 914564 - Do not callback when screen is changed once menu is hidden. r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/ea278845db18
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 914564 - Do not callback when screen is changed once menu is hidden.

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https://hg.mozilla.org/integration/gaia-central/rev/5bc7e12c385a
Author: Gabriele Svelto <gsvelto@mozilla.com>
Desc: Merge pull request #12117 from gabrielesvelto/bug-914731

Bug 914731 - Serialize the webapp optimization and packaging steps r=yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/a94edbb11330
Author: Gabriele Svelto <gabriele.svelto@gmail.com>
Desc: Bug 914731 - Serialize the webapp optimization and packaging steps r=yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/95b68a142bf5
Author: Jan Jongboom <janjongboom@gmail.com>
Desc: Merge pull request #12063 from comoyo/811177_v2

Bug 811177 - Add designmode=on tests to IME tests. r=yxl

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https://hg.mozilla.org/integration/gaia-central/rev/11aa8b878e5f
Author: Jan Jongboom <janjongboom@gmail.com>
Desc: Bug 811177 - Add designmode=on tests to IME tests