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

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https://hg.mozilla.org/integration/gaia-central/rev/6848f14fe19d
Author: Fernando Jiménez Moreno <ferjmoreno@gmail.com>
Desc: Merge pull request #12578 from ferjm/bug920851.mozbrowser.trustedui

Bug 920851 - Listen to mozbrowser events on iframes embedded within the ...

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https://hg.mozilla.org/integration/gaia-central/rev/b50b0331c80e
Author: Fernando Jiménez <ferjmoreno@gmail.com>
Desc: Bug 920851 - Listen to mozbrowser events on iframes embedded within the trusted UI instead of on the trusted UI iframe itself. r=vingtetun

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "60fb11eecd6d06656b3d017acb293bb97a9f63eb", 
+    "revision": "6848f14fe19d5fff23cf329d6f461144a1595052", 
     "repo_path": "/integration/gaia-central"
 }