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

========

https://hg.mozilla.org/integration/gaia-central/rev/3a9f9c152429
Author: John Hu <johu@mozilla.com>
Desc: Merge pull request #25641 from huchengtw-moz/bug-1090810-use-settings-cache

Bug 1090810 - [Stingray] add SettingsCache to smart system, r=rexboy

========

https://hg.mozilla.org/integration/gaia-central/rev/8a2f39fc25d8
Author: John Hu <johu@mozilla.com>
Desc: Bug 1090810 - [Stingray] add SettingsCache to smart system

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "911dd4c192752775fd604f6c31588c17716e8819", 
+    "revision": "3a9f9c152429a9f498f1fd0ca51db0633de49c3a", 
     "repo_path": "/integration/gaia-central"
 }