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

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https://hg.mozilla.org/integration/gaia-central/rev/7530f9702749
Author: Yuren Ju <yurenju@gmail.com>
Desc: Merge pull request #10694 from yurenju/885676

Bug 885676 - Added unit tests for ScreenManager r=alive

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https://hg.mozilla.org/integration/gaia-central/rev/c9464724886c
Author: Yuren Ju <yurenju@gmail.com>
Desc: Bug 885676 - Added unit tests for ScreenManager

b2g/config/gaia.json

@@ -1,4 +1,4 @@
 {
-    "revision": "abc7e68a07eb670a4945b7af01623eb7a886ecf9", 
+    "revision": "7530f9702749c29e4b22f4b85fa73e7106eb6288", 
     "repo_path": "/integration/gaia-central"
 }