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The targeter can be null and in that case it should use the parents.

Bug: b/157910224
Test: covered by unittest. also tested manually. see bug for repro step.
Change-Id: I13db092a6ee062ef9547aec70b6f7cd077558e2d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2225854
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Jesse Schettler <jschettler@chromium.org>
Cr-Commit-Position: refs/heads/master@{#774375}