Remove redundant echo.mojom, verify non-nullables in echo_service.mojom
While looking at mojom files I'm nominally the owner of, I realized
that one had become redundant. So, I just deleted it and checked the
other to make sure it had the right 'nullability' on the method args.
Also moved around code to build against the de-duped mojom file.
BUG=407673
TEST=build with gyp and gn
Review URL: https://codereview.chromium.org/503363004
Cr-Commit-Position: refs/heads/master@{#292054}
CrOS-Libchrome-Original-Commit: 0e989ee10367671221add030b0cb55e42311faf1
5 files changed