Bumping gaia.json for 1 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/d9c7a3149557
Author: Vivien Nicolas <vnicolas@mozilla.com>
Desc:  Bug 1029853 - Hide open browser screens when browser invoked via activity. r=daleharvey

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "5b71834a293a2be988f554bd6f76c932b11a35c3", 
+    "revision": "d9c7a314955707819539439cc4ec68b6fab0639e", 
     "repo_path": "/integration/gaia-central"
 }