Revert "[LayoutNG] Remove optimization that practically does nothing."

This reverts commit fea62cfdaabcc8130c133ce0b9981921e352dcdf.

Reason for revert: Turns out this optimization was important for all the float tests.

Original change's description:
> [LayoutNG] Remove optimization that practically does nothing.
> 
> This was an over-otimization, which realistically probably never gets
> hit.
> 
> Bug: 635619
> Change-Id: Icac53b8605e56242b8455228d0767b2dafb66b5d
> Reviewed-on: https://chromium-review.googlesource.com/c/1305133
> Commit-Queue: Morten Stenshorne <mstensho@chromium.org>
> Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#604211}

TBR=ikilpatrick@chromium.org,mstensho@chromium.org

Change-Id: Id842627640dec23519c0b3de88b07958667e54ea
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 635619
Reviewed-on: https://chromium-review.googlesource.com/c/1311794
Reviewed-by: Ian Kilpatrick <ikilpatrick@chromium.org>
Reviewed-by: Morten Stenshorne <mstensho@chromium.org>
Reviewed-by: Emil A Eklund <eae@chromium.org>
Commit-Queue: Ian Kilpatrick <ikilpatrick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604439}
1 file changed