https://chromium-review.googlesource.com/c/chromium/mini_chromium/+/899847
turns the warning on. This adds one annotation, and fixes one bug.
Includes mini_chromium roll:
.../mini_chromium$ git log 5fcfa43c1587b94132e24782579350cb8266b990..3b953302848580cdf23b50402befc0ae09d03ff9 --oneline
3b95330 (HEAD, origin/master, origin/HEAD) Add -Wimplicit-fallthrough when building on clang
Bug: chromium:807632
Change-Id: I2f3ddca0228e52013844cb8d78d10cb359e851d0
Reviewed-on: https://chromium-review.googlesource.com/900317
Commit-Queue: Scott Graham <scottmg@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>