Mark...

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/1297750Reviewed-by: Alan Cutter <alancutter@chromium.org>
Commit-Queue: Alan Cutter <alancutter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#602262}

third_party/WebKit/LayoutTests/TestExpectations

@@ -5466,3 +5466,4 @@ crbug.com/898378 [ Mac10.13 ] fast/scroll-behavior/smooth-scroll/keyboard-scroll
 
 # Sheriff 2018-10-24
 crbug.com/898394 [ Linux ] virtual/android/url-bar/bottom-and-top-fixed-sticks-to-top.html [ Failure ]
+crbug.com/898378 [ Mac10.13 ] virtual/scroll_customization/fast/scroll-behavior/smooth-scroll/keyboard-scroll.html [ Timeout ]