Disable flaky f/e/middleClickAutoscroll-nested-divs-forbidden.html (Mac)

TBR=sahel@chromium.org
NOTRY=true

Bug: 872635,872632
Change-Id: I59bb656ad0047c7391d96a6b59e1358af91a7b17
Reviewed-on: https://chromium-review.googlesource.com/1169002Reviewed-by: vitaliii <vitaliii@chromium.org>
Commit-Queue: vitaliii <vitaliii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581832}

third_party/WebKit/LayoutTests/TestExpectations

@@ -4871,7 +4871,7 @@ crbug.com/851090 [ Mac ] virtual/mouseevent_fractional/fast/events/middleClickAu
 crbug.com/851090 [ Mac ] fast/events/middleClickAutoscroll-nested-divs.html [ Failure Pass ]
 crbug.com/851090 [ Mac ] virtual/user-activation-v2/fast/events/autoscroll-over-scrollbar.html [ Failure Pass ]
 
-# Sherrif 2018-08-08
+# Sheriff 2018-08-08
 crbug.com/871105 [ Linux ] svg/dom/remove-use-target-element-indirectly.html [ Pass Crash ]
 crbug.com/872025 [ Mac Linux ] fast/css-grid-layout/crash-large-positions.html [ Pass Timeout ]
 crbug.com/871416 fast/spatial-navigation/snav-stay-in-overflow-div.html [ Pass Failure ]
@@ -4879,3 +4879,6 @@ crbug.com/872242 [ Mac ] fast/events/autoscroll-over-scrollbar.html [ Pass Failu
 
 # Only passes on bots with GPUs.
 crbug.com/871445 [ Mac ] http/tests/media/video-load-metadata-decode-error.html [ Timeout ]
+
+# Sheriff 2018-08-09
+crbug.com/872635 [ Mac ] fast/events/middleClickAutoscroll-nested-divs-forbidden.html [ Failure Pass ]