Fix implicit-fallthrough warnings. DO NOT MERGE.

These changes are not needed in goog/master.

Test: make checkbuild
Bug: 112564944
Change-Id: I75972e680c9502e1b83845f08e79b99a8084cc4c
(cherry picked from commit df891f8a31daafe488c00bb95a5afff14af83e43)
Exempt-From-Owner-Approval: do not block on new warnings
2 files changed