Revert "[SpatNav] Account for clipping in z-ordering checks"

This reverts commit b72c9e10a746d28aef4e1c9b5cf669e3b4f8f637.

Reason for revert: Causes fast/spatial-navigation/snav-stay-in-overflow-div.html to fail on Mac bots.

Original change's description:
> [SpatNav] Account for clipping in z-ordering checks
> 
> The spatial navigation algorithm attempts to prioritize targets fully
> contained within another target. However, the current implementation has
> a bug because it uses unclipped rects to determine containment.
> 
> This CL fixes the issue by using MapToVisualRectInAncestorSpace which
> does account for clipping.
> 
> Small cleanup: Remove the |ignore_border| option since it's always true.
> 
> Bug: 957240
> Change-Id: Id032bb9d354ec06d075b2de6bd53a8799f7a8af1
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1586660
> Reviewed-by: Emil A Eklund <eae@chromium.org>
> Commit-Queue: David Bokan <bokan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#654878}

TBR=bokan@chromium.org,eae@chromium.org

Change-Id: Ibfc55d241dbebcdd203f8a6f5df0f90d34c1c02b
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 957240, 957696
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1588726
Reviewed-by: Adithya Srinivasan <adithyas@chromium.org>
Commit-Queue: Adithya Srinivasan <adithyas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654982}