Disable TopControlsSlideControllerTest.TestScrollingMaximizedPageBeforeGoingToTabletMode on mash

Consistently failing since
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Mojo%20ChromiumOS/34744

Bug: 866991
Change-Id: Idd9ea206c37b53fd0b2d8fa516c8cb486d1eb7b6
Reviewed-on: https://chromium-review.googlesource.com/1225100Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Chong Zhang <chongz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591214}

testing/buildbot/filters/chromeos.mash.fyi.browser_tests.filter

@@ -38,6 +38,7 @@
 -BrowserNonClientFrameViewAshTest.HeaderHeightForSnappedBrowserInSplitView/*
 
 # Touch gestures don't work in webcontents. https://crbug.com/866991.
+-TopControlsSlideControllerTest.TestScrollingMaximizedPageBeforeGoingToTabletMode
 -TopControlsSlideControllerTest.TestScrollingPage
 -TopControlsSlideControllerTest.TestScrollingPageAndSwitchingToNTP
 -TopControlsSlideControllerTest.TestClosingATab