Update layout tree rebuild root after removing pseudo element.

We tried to avoid marking the pseudo element when it was about to be
removed, but the pseudo element earlied out before removal if it wasn't
marked for re-attachment causing the element not to be removed.

Notify the StyleEngine about removal instead, so that it can update the
traversal root. For normal elements the StyleEngine is notified through
ChildrenRemoved().

Bug: 989894
Change-Id: Ia2bf52c9bed157c4ac806a10b9367b0f99038974
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1732096
Reviewed-by: Anders Hartvoll Ruud <andruud@chromium.org>
Commit-Queue: Rune Lillesveen <futhark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683543}
3 files changed