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

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https://hg.mozilla.org/integration/gaia-central/rev/67cb3ced85f8
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #21792 from davidflanagan/bug1037097

Bug 1037097: restrict image decode size in MediaFrame based on device memory size

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https://hg.mozilla.org/integration/gaia-central/rev/1986368a4663
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Bug 1037097: restrict image decode size in MediaFrame based on device memory size

add unit tests

b2g/config/gaia.json

@@ -4,6 +4,6 @@
         "remote": "", 
         "branch": ""
     }, 
-    "revision": "bf43989425f480efd7fc9aeece27207520d4ad5c", 
+    "revision": "67cb3ced85f8517e1f6ab20b60eba7dd18933bce", 
     "repo_path": "/integration/gaia-central"
 }