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

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https://hg.mozilla.org/integration/gaia-central/rev/cdbf28c5ea80
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #12468 from crdlc/bug-920960

Bug 920960 - Page test fails when it is launched isolated

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https://hg.mozilla.org/integration/gaia-central/rev/7e78f0cbff2f
Author: crdlc <crdlc@tid.es>
Desc: Bug 920960 - Page test fails when it is launched isolated