Hey , I think this is meant to be internal so it shouldn't be in the public interface. Can you either revert it or annotate it as such. Sorry about this, but it shouldn't have been filed to you.
Fixed
Pinned fields
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RFC: https://docs.google.com/document/d/1QccFEvHWEL2-ldS_aTfjphYJGB4YVmMKrMB-UyL2KFI/edit