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

========

https://hg.mozilla.org/integration/gaia-central/rev/b31db82c674b
Author: autolander <bug.autolander@gmail.com>
Desc: Bug 1156141 - merge pull request #29677 from msliu:Bug-1156141-fix to mozilla-b2g:master

========

https://hg.mozilla.org/integration/gaia-central/rev/9235dde1ed9a
Author: vliu <vliu@mozilla.com>
Desc: Bug 1156141 - Make switch from boot animation to first system app screen seamlessly. r=alive

b2g/config/gaia.json

@@ -1,9 +1,9 @@
 {
     "git": {
-        "git_revision": "f78ac92796e3aaf3000382886d7ce9be63aae4e7", 
+        "git_revision": "bd4cb1a4d5889e54cd94599a6f545280428e51df", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "5898418dd6ecf29e39b1f11513b9bd4d797e9eed", 
+    "revision": "b31db82c674b21ac9e833724d4a2d7cbf3cd44b1", 
     "repo_path": "integration/gaia-central"
 }