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

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https://hg.mozilla.org/integration/gaia-central/rev/db7fa728f0b1
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #16137 from crdlc/bug-970340

Bug 970340 - [Download Manager]A file with a size >1GB is not displayed ...

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https://hg.mozilla.org/integration/gaia-central/rev/8cd2ab1745eb
Author: crdlc <crdlc@tid.es>
Desc: Bug 970340 - [Download Manager]A file with a size >1GB is not displayed successfully

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https://hg.mozilla.org/integration/gaia-central/rev/03b11c7e05b3
Author: Cristian Rodriguez <crdlc@tid.es>
Desc: Merge pull request #16488 from crdlc/bug-970835

Bug 970835 - [Contacts] The selection of contacts is slow AND scroll too...

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https://hg.mozilla.org/integration/gaia-central/rev/5e256dee6564
Author: crdlc <crdlc@tid.es>
Desc: Bug 970835 - [Contacts] The selection of contacts is slow AND scroll too when there are a lot of contacts to import
Bumping manifests a=b2g-bump