This test is consistently slow on Mac 10.13. See https://test-results.appspot.com/dashboards/flakiness_dashboard.html#tests=fast%2Fscroll-behavior%2Fsmooth-scroll%2Fkeyboard-scroll.html&testType=webkit_layout_tests

sahel@, PTAL.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/00a07783f8a18b843ac85f2bac3b259ec50c96e9

commit 00a07783f8a18b843ac85f2bac3b259ec50c96e9
Author: Yi Gu <yigu@chromium.org>
Date: Wed Oct 24 02:49:49 2018

Mark fast/scroll-behavior/smooth-scroll/keyboard-scroll.html slow

This test is consistently slow on Mac 10.13.

TBR=sahel@chromium.org
NOTRY=true

Bug: 898378
Change-Id: I09c144a06023918f6b4965409cecdb7743c095dc
Reviewed-on: https://chromium-review.googlesource.com/c/1297733
Reviewed-by: Yi Gu <yigu@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602228}
[modify] https://crrev.com/00a07783f8a18b843ac85f2bac3b259ec50c96e9/third_party/WebKit/LayoutTests/TestExpectations

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0210aba4c9c2df5423cdf4272e55aa1cf6fe6498

commit 0210aba4c9c2df5423cdf4272e55aa1cf6fe6498
Author: Alan Cutter <alancutter@chromium.org>
Date: Wed Oct 24 06:05:35 2018

Mark virtual/scroll_customization/fast/scroll-behavior/smooth-scroll/keyboard-scroll.html as timing out

This is a follow up to https://chromium-review.googlesource.com/c/1297733 to also
cover the virtual version of this test.

TBR=sahel@chromium.org
NOTRY=true

Bug: 898378
Change-Id: I2c9748f00f6e58b287c0f50c2b68f312d104dd2c
Reviewed-on: https://chromium-review.googlesource.com/c/1297750
Reviewed-by: Alan Cutter <alancutter@chromium.org>
Commit-Queue: Alan Cutter <alancutter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602262}
[modify] https://crrev.com/0210aba4c9c2df5423cdf4272e55aa1cf6fe6498/third_party/WebKit/LayoutTests/TestExpectations