Link perf_tests OWNERS over to DOM OWNERS

Change-Id: Ib32c839baee0be8e5a9785a5df85774f61c337c6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2429374
Commit-Queue: Mason Freed <masonfreed@chromium.org>
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Auto-Submit: Mason Freed <masonfreed@chromium.org>
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#810309}

third_party/blink/perf_tests/dom/OWNERS

+file://third_party/blink/renderer/core/dom/OWNERS

third_party/blink/perf_tests/parser/OWNERS

+file://third_party/blink/renderer/core/html/parser/OWNERS

third_party/blink/perf_tests/shadow_dom/OWNERS

+file://third_party/blink/renderer/core/dom/OWNERS