Bumping gaia.json for 2 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/52a3492784fa
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #17370 from alivedise/bugzilla/961800_master_merging/child-window-factory

Bug 961800 - Implement Child Window Factory, r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/a1a234a4883e
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 961800 - Implement Child Window Factory

Conflicts:
	apps/system/js/app_transition_controller.js
	apps/system/js/app_window.js
	apps/system/js/app_window_manager.js
	apps/system/js/cards_view.js
	apps/system/style/window.css
Bumping manifests a=b2g-bump