Revert "Update D8 R8 to 8.6.4-dev"

Revert submission 3094947-update-r8

Reason for revert: Cause of runtime performance regression b/342492570

Reverted changes: /q/submissionid:3094947-update-r8

Change-Id: Ic17b9c7972d7e1bd483421e59a108dd61d57188f
4 files changed