Revert change preferring LayoutTreeBuilder tree, and dependent changes.

Original reviews:
https://chromium-review.googlesource.com/c/chromium/src/+/1206050
https://chromium-review.googlesource.com/c/chromium/src/+/1242572
https://chromium-review.googlesource.com/c/chromium/src/+/1345714

TBR=dmazzoni@chromium.org

Bug: 906310, 908916
Change-Id: Ie56e5030db4bb3039816c5d5d9576279435835e6
Reviewed-on: https://chromium-review.googlesource.com/c/1353062
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Alice Boxhall <aboxhall@chromium.org>
Commit-Queue: Alice Boxhall <aboxhall@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612411}
31 files changed