Add "# COMPONENT" to OWNERS files

Most files in this CL either use "Build" or "Test" components

See https://tinyurl.com/yxau5sc4 for context.

Bug: 977050
Change-Id: I1ab5e956e11553ad6ca548ac0bd4669daeb631ff
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1808169
Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Eric Foo <efoo@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#703516}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 5a6ecf934cc33faea94856484245cbf97f255ef5