Bumping gaia.json for 3 gaia-central revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/dc22cb96998e
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Merge pull request #13368 from eeejay/bug-920839

Bug 920839 - Value Selector accessibility improvements. r=timdream

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https://hg.mozilla.org/integration/gaia-central/rev/1a2ebd989db0
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 920839 - Added spinbutton ARIA markup to value picker.

========

https://hg.mozilla.org/integration/gaia-central/rev/1cff0273e0b1
Author: Eitan Isaacson <eitan@monotonous.org>
Desc: Bug 920839 - ARIA fixes to value selector.

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "0fd1663337729c472ed0b49036540fbc1f4852ac", 
+    "revision": "dc22cb96998eff0cab1f4efba87cb74aa1f98281", 
     "repo_path": "/integration/gaia-central"
 }