Revert "Remove legacy-data-mixin"
Revert "Remove legacy-data-mixin"

This reverts commit 55f0ffa508fcde51405b385f2a44aeb321a07633.

Reason for revert: legacyUndefinedCheck is required for now

Change-Id: Id8eb5b632e46ed8301c48660f559bd35816836c8

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