Mark fast/events/middleClickAutoscroll-latching.html timeout

See
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mac10.13%20Tests%20%28dbg%29/4709

TBR=wjmaclean@chromium.org
NOTRY=true

Bug: 827209
Change-Id: Ife32a29fc4928d037246bd20488917860807366d
Reviewed-on: https://chromium-review.googlesource.com/1175698
Commit-Queue: Xida Chen <xidachen@chromium.org>
Reviewed-by: Xida Chen <xidachen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#583231}

third_party/WebKit/LayoutTests/TestExpectations

@@ -4493,7 +4493,7 @@ crbug.com/754986 virtual/video-surface-layer/media/video-transformed.html [ Pass
 
 # Sheriff 2018-03-29
 crbug.com/827088 bluetooth/requestDevice/chooser/new-scan-device-added.html [ Pass Crash ]
-crbug.com/827209 fast/events/middleClickAutoscroll-latching.html [ Pass Failure ]
+crbug.com/827209 fast/events/middleClickAutoscroll-latching.html [ Pass Failure Timeout ]
 crbug.com/827209 virtual/mouseevent_fractional/fast/events/middleClickAutoscroll-latching.html [ Pass Failure ]
 # Sheriff 2018-08-14
 crbug.com/827209 virtual/user-activation-v2/fast/events/middleClickAutoscroll-latching.html [ Pass Timeout Failure ]