Add a description for --show-taps.

BUG=none

Change-Id: I37e27f6c46b5ee034ff3d508186a13494b7a1cac
Reviewed-on: https://chromium-review.googlesource.com/c/1461324
Commit-Queue: Avi Drissman <avi@chromium.org>
Commit-Queue: James Cook <jamescook@chromium.org>
Auto-Submit: Avi Drissman <avi@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#630530}
1 file changed