Bumping gaia.json for 3 gaia revision(s) a=gaia-bump

========

https://hg.mozilla.org/integration/gaia-central/rev/0838151416d2
Author: Marshall Culpepper <marshall.law@gmail.com>
Desc: Merge pull request #21215 from marshall/bug982663_metricsAppUsage

Bug 982663: Collect and report app usage data

========

https://hg.mozilla.org/integration/gaia-central/rev/3f5f9ae97be0
Author: Marshall Culpepper <marshall@mozilla.com>
Desc: Bug 982663: Part 2 - Integration tests and follow up for App Usage metrics. r=etienne

* Use ftu.pingURL as the default base URL for app usage metrics
* Added tests for app usage default values
* Use manifestURL instead of origin to track unique apps

========

https://hg.mozilla.org/integration/gaia-central/rev/dba5b4a3f2ac
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Bug 982663: Part 1 - Collect and report app usage data. r=etienne

* record app installation and uninstallation
* send a unique device id with each report
* report deviceinfo, language and screen data, and make telemetry parameters
  configurable through settings
* Refactor to match system app module structure
* Unit tests and bug fixes
* Change strings in Settings and FTU apps to mention app usage data collection
* Address review comments
* Fix failing bootstrap tests

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "2845edfa1dd82f308f1ce5cc7e29397e0d420434", 
+    "revision": "0838151416d274d392f4216d50b5bf219ca63737", 
     "repo_path": "/integration/gaia-central"
 }