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

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https://hg.mozilla.org/integration/gaia-central/rev/efaae1b2b4a4
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Merge pull request #14852 from etiennesegonzac/bug-944697-edge-gesture-marionette-retina

Bug 944697 - Make the edge_gesture_test.js resolution independent.

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https://hg.mozilla.org/integration/gaia-central/rev/28d169d67ca1
Author: Etienne Segonzac <etienne@segonzac.info>
Desc: Bug 944697 - Make the edge_gesture_test.js resolution independent. r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/122f9f5d67d2
Author: lissyx <lissyx+github@lissyx.dyndns.org>
Desc: Merge pull request #15063 from lissyx/bug956588

Bug 956588 - Make sure that we pass a blob when setting wallpaper r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/e05aac0e9ed6
Author: Alexandre Lissy <lissyx+github@lissyx.dyndns.org>
Desc: Bug 956588 - Make sure that we pass a blob when setting wallpaper

Bug 943246 removed the checking on strings. Turns out that we do want
this. So we re-introduce this, and if the wallpaper is a data URI we
directly use it.