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

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https://hg.mozilla.org/integration/gaia-central/rev/8ef61794ca26
Author: Ghislain 'Aus' Lacroix <aus@noiseport.org>
Desc: Merge pull request #26598 from nullaus/bug1100714

Bug1100714

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https://hg.mozilla.org/integration/gaia-central/rev/9cdcd2f48250
Author: Ghislain 'Aus' Lacroix <aus@mozilla.com>
Desc: bug 1100714 - PopupWindow class should use rearWindow for appChrome r=alive
Bumping manifests a=b2g-bump