Re-land: Move focus rings and highlight layers under accessibility bubbles.

Original patch: http://crrev.com/c/2568547
Revert: http://crrev.com/c/2583106

Fix for issue where focus ring appears below switch access panel. Now clients can specify if they want their focus ring to appear above or below accessibility bubble panels. STS will specify they appear below, though other clients will (by default) specify they appear above all panels. This fixes an issue with the switch access focus ring didn't appear above the switch access panel.

Original description:

Move focus rings and highlight layers under accessibility bubbles.

Will allow Select-to-speak panel UI to appear above focus ring and highlight layers. This also avoids the need to create more window containers.

Bug: 1157261, 1143814
Change-Id: Ibd8dd577ecd4fb5767b628c2eff679a2f6931b9c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2582997
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Joel Riley <joelriley@google.com>
Cr-Commit-Position: refs/heads/master@{#836222}