GitLab

- Formalize coordinate space of subframe placeholders to be in their parent's space.

Bug: 1009552
Change-Id: I75c44a648acc18696e019c669d850bc842823af4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2363875Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#801354}