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

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https://hg.mozilla.org/integration/gaia-central/rev/ec20da95a33c
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #16888 from alivedise/bugzilla/977934_master/render_activity_inside_caller

Bug 977934 - Render activity inside caller, r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/618cd111be20
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 977934 - Render activity frame inside its caller
Bumping manifests a=b2g-bump