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

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https://hg.mozilla.org/integration/gaia-central/rev/b3a6e363c1da
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Merge pull request #19136 from KevinGrandon/bug_1005511_jshint_shared_device_storage

Bug 1005511 - JSHint fixes for shared/js/device_storage/

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https://hg.mozilla.org/integration/gaia-central/rev/6fc4f8c3d95a
Author: Kevin Grandon <kevingrandon@yahoo.com>
Desc: Bug 1005511 - JSHint fixes for shared/js/device_storage/ r=djf

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https://hg.mozilla.org/integration/gaia-central/rev/dbaef087b319
Author: George <georgeiscoming@gmail.com>
Desc: Merge pull request #19185 from cctuan/987487

Bug 987487 - [Gaia] [Build] Refactoring webapp-optimize.js and unit tests

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https://hg.mozilla.org/integration/gaia-central/rev/e244ff526b0a
Author: cctuan <georgeiscoming@gmail.com>
Desc: Bug 987487 - [Gaia] [Build] Refactoring webapp-optimize.js and unit tests
Bumping manifests a=b2g-bump