Reland "Updates the bottom border to be 15% black instead of black."

This reverts commit 4205d6e8d3370bc816d722e908a372921936dd8a.

Reason for reland : didn't fix it.

Original change's description:
> Revert "Updates the bottom border to be 15% black instead of black."
> 
> This reverts commit f3a6c253c7ae2eb42dd58de281587dbf110ef493.
> 
> Reason for revert: suspected for https://bugs.chromium.org/p/chromium/issues/detail?id=923894#c14
> 
> Original change's description:
> > Updates the bottom border to be 15% black instead of black.
> > 
> > This is a UX issue that came up during https://crbug.com/918788
> > 
> > Bug: 853593
> > Change-Id: If0efdba2d344ee379fb560c61dc43ea4a14c0510
> > Reviewed-on: https://chromium-review.googlesource.com/c/1415232
> > Commit-Queue: Jay Harris <harrisjay@chromium.org>
> > Reviewed-by: Bret Sepulveda <bsep@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#624515}
> 
> TBR=bsep@chromium.org,harrisjay@chromium.org
> 
> Change-Id: I7ff365b2fcfafdbd75f6bd506c56f07ab806579d
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 853593, 923894
> Reviewed-on: https://chromium-review.googlesource.com/c/1425997
> Reviewed-by: Gabriel Charette <gab@chromium.org>
> Commit-Queue: Gabriel Charette <gab@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#624635}

TBR=gab@chromium.org,bsep@chromium.org,harrisjay@chromium.org

Change-Id: I6011811309c67dde14d7e390f8aabba54c5db111
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 853593, 923894
Reviewed-on: https://chromium-review.googlesource.com/c/1426013
Commit-Queue: Gabriel Charette <gab@chromium.org>
Reviewed-by: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/master@{#624677}
1 file changed