Explicitly pass -Wno-unused-function to the targets that need it.

Currently, it's disabled globally, but that'll hopefully change soon.
No intended behavior change.

BUG=505316

Review URL: https://codereview.chromium.org/1269293003

Cr-Original-Commit-Position: refs/heads/master@{#344097}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: b2105710d8eab709b51cd3c5a5d974eb544d16d5
2 files changed