fix switch fallthrough warning

Bug: skia:
Change-Id: Ia2e25545319d54c3258b76c050b46a73c292c791
Reviewed-on: https://skia-review.googlesource.com/115085
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Ethan Nicholas <ethannicholas@google.com>
1 file changed