Bumping gaia.json for 4 gaia revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-central/rev/f2ce7eff25a7
Author: John Hu <johu@mozilla.com>
Desc: Merge pull request #28781 from huchengtw-moz/bug-1141887-app-window-focus

Bug 1141887 - [Stingray] apply focus manager to app window related UIs, r=lchang, r=sungchiu

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https://hg.mozilla.org/integration/gaia-central/rev/176b02d8f593
Author: John Hu <johu@mozilla.com>
Desc: Bug 1141887 - [Stingray] apply focus manager to app window related UIs

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https://hg.mozilla.org/integration/gaia-central/rev/c2a8446ff3a8
Author: Ian Liu <iliu@mozilla.com>
Desc: Merge pull request #28884 from ian-liu/bluetooth/bug1140247_handle_no_filepath_for_file_sending

Bug 1140247 - check filepath existed or not before browse file from device storage, r=djf

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https://hg.mozilla.org/integration/gaia-central/rev/895e8150045a
Author: ian-liu <iliu@mozilla.com>
Desc: bug 1140247 - check filepath existed or not before browse file from device storage, r=djf

b2g/config/gaia.json

@@ -1,9 +1,9 @@
 {
     "git": {
-        "git_revision": "738987bd80b0ddb4ccf853855388c2627e19dcc1", 
+        "git_revision": "77c27e22b05f8bc78aea65cf559b52ca89833c20", 
         "remote": "https://git.mozilla.org/releases/gaia.git", 
         "branch": ""
     }, 
-    "revision": "00ea00a8e98d73a6556ece5d68c781fefec93810", 
+    "revision": "f2ce7eff25a73a6bb699f1413694f5d9405bef44", 
     "repo_path": "integration/gaia-central"
 }