Make gn gen --check pass for third_party/ced

All but one public header file were inaccessible to ced_unittests

Bug: 1159032
Change-Id: I5f47f11bbfd29d5b49abeeab5e01a65bf6e21375
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2671501
Reviewed-by: Dirk Pranke <dpranke@google.com>
Reviewed-by: Erik Staab <estaab@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#850263}
GitOrigin-RevId: db51074c73719b212c4a0e9e837004c6ec3098dc
1 file changed