Fix implicit-fallthrough warnings. DO NOT MERGE.

These changes are not needed in goog/master.

Test: make checkbuild
Bug: 112564944
Change-Id: I02d5cdaacecf06994f6c26328533eccf511009bb
(cherry picked from commit 03ef7ffc93e07f59bb5a329b57a9b2006b39af0d)
Exempt-From-Owner-Approval: do not block on new warnings
1 file changed