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

========

https://hg.mozilla.org/integration/gaia-central/rev/6c394d3b633a
Author: Wilson Page <wilsonpage@me.com>
Desc: Merge pull request #18029 from wilsonpage/988670

Bug 988670 - [Camera][Madai] Behavior when leaving camera while in previ...

========

https://hg.mozilla.org/integration/gaia-central/rev/87c0bf8371e6
Author: hyuna.cho <hyuna.cho@lge.com>
Desc: Bug 988670 - [Camera][Madai] Behavior when leaving camera while in preview mode and hitting home button needs to be reconsidered

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "9079aed1a902234596b31ca4964205bbefcbec06", 
+    "revision": "6c394d3b633a42b1515d220b486e9ad243748bcd", 
     "repo_path": "/integration/gaia-central"
 }