build cromo with explicit public visibility

BUG=chromium:313434
TEST=`emerge-x86-alex cromo` doesn't issue build warnings

Change-Id: I45359a7f6fa749b72205d26c6035151eca0d1abe
Reviewed-on: https://chromium-review.googlesource.com/183881
Reviewed-by: Ben Chan <benchan@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
1 file changed