Bumping gaia.json for 4 gaia-central revision(s)

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https://hg.mozilla.org/integration/gaia-central/rev/f53a55fb7dba
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #11423 from crh0716/900874

Bug 900874 - Register to DOM events instead of system messages r=evelyn

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https://hg.mozilla.org/integration/gaia-central/rev/c70b822c886e
Author: crh0716 <crh0716@gmail.com>
Desc: Bug 900874 - Register to DOM events instead of system messages

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https://hg.mozilla.org/integration/gaia-central/rev/e7560439092a
Author: Arthur Chen <crh0716@gmail.com>
Desc: Merge pull request #11449 from crh0716/903181

Bug 903181 - Add a step value r=evelyn

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https://hg.mozilla.org/integration/gaia-central/rev/811120d1f1aa
Author: crh0716 <crh0716@gmail.com>
Desc: Bug 903181 - Add a step value