[reading-order-items] Grid Order Backward Navigation
This patch updates the logic in FocusController so we can navigate
backward in a reading order container with CSS rule
reading-order-items: grid-order. The feature is guarded behind the
flag CSSReadingOrderItemsEnabled.
Note that focus across display: contents isn't fully supported yet.
Change-Id: Idefbb6d8ea72b6da49a2a57b8698610b9017ef40
Bug: 40932006
Bug: 336358906
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5483668
Commit-Queue: Di Zhang dizhangg@chromium.org
Reviewed-by: Mason Freed masonf@chromium.org
Cr-Commit-Position: refs/heads/main@{#1298919}