Bumping gaia.json for 2 gaia-1_3 revision(s) a=gaia-bump

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https://hg.mozilla.org/integration/gaia-1_3/rev/04abb059a9e0
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Merge pull request #16148 from davidflanagan/bug963917-v1.3-3

Bug 963917: reduce Gallery memory use (and fix leak) while scanning r=dkuo

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https://hg.mozilla.org/integration/gaia-1_3/rev/c4932dd24b69
Author: David Flanagan <dflanagan@mozilla.com>
Desc: Bug 963917: reduce Gallery memory use (and fix leak) while scanning

force software canvases for thumbnail and preview creation with willReadFrequently

Free canvas memory after creating a thumbnail

Make sure our thumbnail blobs are file-backed not memory-backed

update mediadb docs