Based on #1498634: [meta] Define revision/translation SQL schema for core entities (no patch) there should be a new schema. The name should be file_managed_translation it's connected to file_managed directly.
Here is a first patch. I wasn't able to find a column which wouldn't make sense to be translatable.
Update functions should clearly not use dynamic schema information. If this update function is used later, it would create a different schema. We have a practice of hardwiring all information needed for an update function to ensure it does the same thing regardless of time it ran.
Also mark for the sprint board.
Moving this off sprint since looks like #1498634: [meta] Define revision/translation SQL schema for core entities (no patch) needs some more discussion in regards to revisions.
Retitle based on #1658712: Refactor test_entity schema to be multilingual. Marking postponed on #1691952: Make EntityFieldQuery work with multilingual properties.
#1691952: Make EntityFieldQuery work with multilingual properties is fixed.
The (core) file entity is not translatable, so no need to change its default schema.
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