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

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https://hg.mozilla.org/integration/gaia-central/rev/ae263cdfa1ca
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #13132 from dwi2/bug922540

Bug 922540 - rewrite build/additional-extensions.py in javascript r=yurenju

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https://hg.mozilla.org/integration/gaia-central/rev/2998af48691f
Author: tzhuang <tzhuang@mozilla.com>
Desc: Bug 922540 - rewrite build/additional-extensions.py in javascript

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https://hg.mozilla.org/integration/gaia-central/rev/5fb9e61c94a2
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #14036 from KevinGrandon/bug_942955_system_clean_up_window_manager

Bug 942955 - maybeSetFrameIsCritical is unused after activity window refactor r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/f370c7c2943e
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 942955 - maybeSetFrameIsCritical is unused after activity window refactor