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

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https://hg.mozilla.org/integration/gaia-central/rev/4b602663e947
Author: Alive.Kuo <alegnadise@gmail.com>
Desc: Merge pull request #14566 from alivedise/bugzilla/943717/app-window-factory-creation

Bug 943717 - Refine Instantication of AppWindow and ActivityWindow, r=etienne

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https://hg.mozilla.org/integration/gaia-central/rev/dca37d4995f5
Author: Alive Kuo <alegnadise@gmail.com>
Desc: Bug 943717 - Refine Instantication of AppWindow and ActivityWindow

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "3c3706bd5581eb1ff85449470892ae0dabc5ab6b", 
+    "revision": "4b602663e947f6c97d8fbeed277b613844d5beec", 
     "repo_path": "/integration/gaia-central"
 }