Mark fast/scrolling/listbox-wheel-event.html timeout under fast path

The test has been "Timeout" in addition to "Failure":
https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=blink_web_tests%20(with%20patch)&tests=virtual%2Fthreaded-prefer-compositing%2Ffast%2Fscrolling%2Flistbox-wheel-event.html

TBR=mustaq@chromium.org
NOTRY=True

Bug: 841567
Change-Id: Ib8813e61070fbb202a313c9e5f33c56c0026058f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2559090Reviewed-by: Yi Gu <yigu@chromium.org>
Commit-Queue: Yi Gu <yigu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#830675}

third_party/blink/web_tests/TestExpectations

@@ -291,7 +291,7 @@ crbug.com/730267 virtual/gpu-rasterization-disable-yuv/images/yuv-decode-eligibl
 # Flaky virtual/threaded/fast/scrolling tests
 crbug.com/841567 virtual/threaded-prefer-compositing/fast/scrolling/absolute-position-behind-scrollbar.html [ Failure Pass ]
 crbug.com/841567 virtual/threaded-prefer-compositing/fast/scrolling/fixed-position-behind-scrollbar.html [ Failure Pass ]
-crbug.com/841567 virtual/threaded-prefer-compositing/fast/scrolling/listbox-wheel-event.html [ Failure Pass ]
+crbug.com/841567 virtual/threaded-prefer-compositing/fast/scrolling/listbox-wheel-event.html [ Failure Pass Timeout ]
 crbug.com/841567 virtual/threaded-prefer-compositing/fast/scrolling/overflow-scrollability.html [ Failure Pass Timeout ]
 crbug.com/841567 virtual/threaded-prefer-compositing/fast/scrolling/same-page-navigate.html [ Failure Pass ]