GitLab

Fixed positioned elements are not clipped by their ancestors,
except by the rootWebArea. Similarly with absolutely positioned
elements, except if they have an ancestor with some non-static
positioning.

Bug: 792124
Change-Id: I9c31c90fed89179434ae7f89aa18528e929348da
Reviewed-on: https://chromium-review.googlesource.com/809828
Commit-Queue: Katie D <katie@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522162}