[OWNERS tags] Check against multiple teams per component on presubmit

This new check uses the latest automatically generated component map
https://storage.googleapis.com/chromium-owners/component_map.json to
verify that the change does not introduce multiple teams for the same
component.

TBR=ymzhang@chromium.org,stgao@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/2698813008
Cr-Commit-Position: refs/heads/master@{#453784}
2 files changed