Property tree code must account for parent offsets of fixed layers

Even though fixed position layers are constrained to keep a constant
position wrt to their "fixed container," their initial position must
account for the position of layers between them and this container.

BUG=386810

Review URL: https://codereview.chromium.org/967163002

Cr-Commit-Position: refs/heads/master@{#318640}
2 files changed